shall be entitled to a disability insurance benefit (i) for each month beginning with the first month after his waiting period (as defined in subsection (c)(2)) in which he becomes so entitled to such insurance benefits, (ii) in the case of an individual who has been medically determined to have amyotrophic lateral sclerosis, for each month beginning with the first month during all of which the individual is under a disability and in which the individual becomes entitled to such insurance benefits, or (iii) for each month beginning with the first month during all of which he is under a disability and in which he becomes so entitled to such insurance benefits, but only if he was entitled to disability insurance benefits which terminated, or had a period of disability (as defined in section 416(i) of this title) which ceased, within the 60-month period preceding the first month in which he is under such disability, and ending with the month preceding whichever of the following months is the earliest: the month in which he dies, the month in which he attains retirement age (as defined in section 416(l) of this title), or, subject to subsection (e), the termination month. For purposes of the preceding sentence, the termination month for any individual shall be the third month following the month in which his disability ceases; except that, in the case of an individual who has a period of trial work which ends as determined by application of section 422(c)(4)(A) of this title, the termination month shall be the earlier of (I) the third month following the earliest month after the end of such period of trial work with respect to which such individual is determined to no longer be suffering from a disabling physical or mental impairment, or (II) the third month following the earliest month in which such individual engages or is determined able to engage in substantial gainful activity, but in no event earlier than the first month occurring after the 36 months following such period of trial work in which he engages or is determined able to engage in substantial gainful activity. No payment under this paragraph may be made to an individual who would not meet the definition of disability in subsection (d) except for paragraph (1)(B) thereof for any month in which he engages in substantial gainful activity, and no payment may be made for such month under subsection (b), (c), or (d) of section 402 of this title to any person on the basis of the wages and self-employment income of such individual. In the case of a deceased individual, the requirement of subparagraph (C) may be satisfied by an application for benefits filed with respect to such individual within 3 months after the month in which he died.

and as though he had become entitled to old-age insurance benefits in the month in which the application for disability insurance benefits was filed and he was entitled to an old-age insurance benefit for each month for which (pursuant to subsection (b)) he was entitled to a disability insurance benefit. For the purposes of the preceding sentence, in the case of an individual who attained age 62 in or before the first month referred to in subparagraph (A) or (B) of such sentence, as the case may be, the elapsed years referred to in section 415(b)(3) of this title shall not include the year in which he attained age 62, or any year thereafter.