A155090 Composites k such that composite(k) is odd.

4, 8, 12, 15, 21, 26, 30, 33, 35, 38, 40, 44, 46, 49, 55, 58, 63, 66, 68, 70, 77, 81, 84, 86, 88, 90, 92, 94, 100, 102, 106, 108, 110, 112, 116, 118, 121, 123, 126, 129, 134, 136, 140, 142, 144, 146, 150, 154, 156, 158, 160, 162, 165, 169, 171, 176, 180, 183, 185

Offset

1,1

Links

Table of n, a(n) for n=1..59.

Example

4 (composite) is a term because composite(4) = 9;
8 (composite) is a term because composite(8) = 15;
12 (composite) is a term because composite(12) = 21.

Maple

A002808 := proc(n) option remember ; if n = 1 then 4; else for a from procname(n-1)+1 do if not isprime(a) then return a; end if; end do; end if; end proc:
isA002808 := proc(n) n >= 4 and not isprime(n) ; end proc:
for i from 1 to 400 do if isA002808(i) then c := A002808(i) ; if type(c, 'odd') then printf("%d, ", i) ; end if; end if; end do: # R. J. Mathar, May 10 2010

Mathematica

seq[nmax_] := Module[{m, sq, cc}, For[m = nmax, True, m = m+nmax, sq = Select[cc = Select[Range[m], CompositeQ], If[# <= Length[cc], OddQ[cc[[#]]], False]&]; If[Length[sq] > nmax, Return[Take[sq, nmax]]]]];
seq[59] (* Jean-François Alcover, Jul 08 2022 *)

Crossrefs

Cf. A002808.

Sequence in context: A311109 A311110 A311111 * A311112 A311113 A311114

Adjacent sequences: A155087 A155088 A155089 * A155091 A155092 A155093

Keyword

nonn

Author

Juri-Stepan Gerasimov, Jan 20 2009

Extensions

Entries checked by R. J. Mathar, May 10 2010

Name and Example section simplified by Jon E. Schoenfield, Feb 10 2019

Status

approved