A102201 Iccanobirt semiprimes (11 of 15): Semiprime numbers in A102121.

4, 581, 427, 8621, 16342, 253486367, 2219057821, 27297112754, 89359826467, 111725421271, 81491456587747, 65683774724947682, 3657883767310690921, 324958155565178050832783011, 7599185976546928443534740942821, 3638796960899657009455220564046301

Offset

1,1

Links

Table of n, a(n) for n=1..16.

Formula

a(n) = A102121(A102181(n)).

Mathematica

nxt[{a_, b_, c_}]:={b, c, IntegerReverse[c+IntegerReverse[b]+IntegerReverse[a]]}; Select[NestList[nxt, {0, 0, 1}, 50][[;; , 1]], PrimeOmega[#]==2&] (* The program generates the first 10 terms of the sequence. *) (* Harvey P. Dale, Dec 17 2025 *)

Crossrefs

Cf. A001358, A102121, A102181, A102191-A102205.

Sequence in context: A241095 A343474 A177963 * A102204 A086143 A123657

Adjacent sequences: A102198 A102199 A102200 * A102202 A102203 A102204

Keyword

nonn,less,base

Author

Jonathan Vos Post and Ray Chandler, Dec 31 2004

Extensions

Offset changed to 1 and a(16) from Jinyuan Wang, Aug 14 2021

Status

approved