A176658 Numbers k such that semiprime(semiprime(k)) + 1 = semiprime(semiprime(k+1)).

3, 5, 11, 14, 20, 32, 52, 57, 70, 72, 81, 95, 114, 124, 231, 240, 273, 276, 287, 291, 371, 380, 441, 507, 528, 544, 573, 607, 629, 647, 672, 695, 716, 739, 828, 830, 832, 873, 1002, 1035, 1037, 1044, 1100, 1104, 1182, 1208, 1236, 1278, 1321, 1340, 1367, 1522

Offset

1,1

Comments

Numbers k such that A001358(A001358(k)) + 1 = A001358(A001358(k+1)).

Numbers k such that A091022(k) + 1 = A091022(k+1).

Links

Table of n, a(n) for n=1..52.

Example

3 is a term because semiprime(semiprime(3)) + 1 = 25 + 1 = semiprime(semiprime(3+1)).

Maple

A091022 := proc(n) A001358(A001358(n)) ; end proc: isA176658 := proc(n) A091022(n)+1 = A091022(n+1) ; end proc: for n from 1 to 1600 do if isA176658(n) then printf("%d, ", n) ; end if; end do: # R. J. Mathar, Apr 26 2010

Crossrefs

Cf. A001358, A091022.

Sequence in context: A166564 A058595 A154773 * A086284 A376397 A376398

Adjacent sequences: A176655 A176656 A176657 * A176659 A176660 A176661

Keyword

nonn

Author

Juri-Stepan Gerasimov, Apr 23 2010

Extensions

Corrected (72 inserted, 85 replaced by 95, 124 inserted) and extended by R. J. Mathar, Apr 26 2010

Status

approved