

A176658


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


0



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
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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 A136500 A024897
Adjacent sequences: A176655 A176656 A176657 * A176659 A176660 A176661


KEYWORD

nonn


AUTHOR

JuriStepan 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



