A102181 Iccanobirt semiprime indices (11 of 15): Indices of semiprime numbers in A102121.

5, 11, 12, 17, 18, 37, 38, 43, 44, 45, 55, 61, 70, 93, 103, 110, 120, 129, 174, 198, 241, 245, 277, 303, 342, 381, 393, 552, 590, 657, 708

Offset

1,1

Links

Table of n, a(n) for n=1..31.

Formula

A102121(a(n)) = A102201(n).

Mathematica

nxt[{a_, b_, c_}]:={b, c, IntegerReverse[c+IntegerReverse[b]+IntegerReverse[a]]}; Flatten[ Position[NestList[nxt, {0, 0, 1}, 800][[;; , 1]], _?(PrimeOmega[#]==2&)]-1] (* Harvey P. Dale, Mar 23 2023 *)

Crossrefs

Cf. A001358, A102121, A102171-A102185, A102201.

Sequence in context: A030318 A102175 A139200 * A103068 A277136 A176821

Adjacent sequences: A102178 A102179 A102180 * A102182 A102183 A102184

Keyword

nonn,more,less,base

Author

Jonathan Vos Post and Ray Chandler, Dec 31 2004

Extensions

Offset changed to 1 and a(21)-a(31) from Jinyuan Wang, Aug 14 2021

Status

approved