A176650 Numbers k such that nonnegative non-semiprime(k)+3 = nonnegative non-semiprime(k+3).

1, 11, 12, 18, 19, 20, 26, 27, 28, 47, 53, 63, 64, 65, 66, 67, 68, 69, 73, 83, 84, 91, 92, 93, 98, 99, 100, 101, 102, 109, 115, 116, 117, 118, 122, 128, 129, 130, 134, 135, 136, 148, 152, 153, 154, 155, 156, 161, 162, 163, 164, 165, 166, 174, 183, 184, 185, 192, 193

Offset

1,2

Comments

Where nonnegative non-semiprime numbers are zero together with A100959 (i.e., 0, 1, 2, 3, 5, 7, 8, 11, 12, 13, 16, 17, 18, 19, 20, 23, 24, 27, 28, 29, 30, ...).

Links

Jinyuan Wang, Table of n, a(n) for n = 1..10000

Example

1 is a term because nonnegative non-semiprime(1)+3 = 3 = nonnegative non-semiprime(1+3).

Maple

A100959 := proc(n) option remember; if n = 1 then 1; else for a from procname(n-1)+1 do if numtheory[bigomega](a) <> 2 then return a; end if; end do end if; end proc:
nnnspr := proc(n) if n = 1 then 0; else A100959(n-1) ; end if; end proc:
isA176650 := proc(n) nnnspr(n) + 3 = nnnspr(n+3) ; end proc:
for n from 1 to 1200 do if isA176650(n) then printf("%d, ", n) ; end if; end do:
# R. J. Mathar, Apr 26 2010

Mathematica

Join[{1}, Flatten[With[{c=Select[Range[0, 300], PrimeOmega[#]!=2&]}, Position[ Partition [c, 4, 1], _?(#[[1]]+3==#[[4]]&), 1, Heads->False]]]+1] (* Harvey P. Dale, Oct 15 2022 *)

Crossrefs

Cf. A100959 (non-semiprimes).

Sequence in context: A079350 A070605 A087450 * A046465 A134926 A105744

Adjacent sequences: A176647 A176648 A176649 * A176651 A176652 A176653

Keyword

nonn

Author

Juri-Stepan Gerasimov, Apr 22 2010

Extensions

Entries checked by R. J. Mathar, Apr 26 2010

Status

approved