This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A128510 #18 Jan 21 2025 22:24:26
%S A128510 4,6,8,9,10,12,14,16,20,21,25,26,28,33,34,35,36,38,40,42,44,46,50,51,
%T A128510 52,54,55,56,60,64,65,68,72,74,76,80,81,82,85,90,93,95,96,98,100,102,
%U A128510 110,111,115,119,121,122,123,124,126,132,133,135,138,140,143,144,145,146,148,150
%N A128510 Composites c such that c*A001414(c) is adjacent to a prime.
%C A128510 The composites c of A002808 are multiplied by the sum of their prime factors (with multiplicity), and are placed into the sequence if that product is in A045718.
%e A128510 c = 52= A002808(74) has prime factor sum A001414(52) = 17, and 52*17 = 883+1 is one away from the prime 883, which adds 52 to the sequence.
%p A128510 A001414 := proc(n) local fcts,d ; fcts := ifactors(n)[2] ; add(op(1,d)*op(2,d),d=fcts) ; end proc:
%p A128510 isA045718 := proc(n) isprime(n+1) or isprime(n-1) ; end proc:
%p A128510 isA128510 := proc(n) local c; if not isprime(n) then c := n*A001414(n) ; isA045718(c) ; else false; end if ; end proc:
%p A128510 for n from 4 to 500 do if isA128510(n) then printf("%d,",n) ; end if; end do: # _R. J. Mathar_, Nov 02 2009
%Y A128510 Cf. A066073.
%K A128510 nonn,easy
%O A128510 1,1
%A A128510 _J. M. Bergot_, May 07 2007
%E A128510 8 inserted and sequence extended by _R. J. Mathar_, Nov 02 2009