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 A109406 #10 Jan 09 2025 13:20:18
%S A109406 3,4,9,10,11,14,20,28,29,32,34,40,43,44,45,46,50,53,58,59,61,62,63,68,
%T A109406 69,72,74,80,83,86,89,95,99,100,101,105,107,109,111,112,115,116,118,
%U A109406 119,121,123,127,129,130,131,132,136,137,140,144,145,150,151,152,153,155
%N A109406 Numbers m such that (sp(m)+sp(m+1)+sp(m+2))/3 is an integer, where sp(n) = n-th semiprime.
%H A109406 Harvey P. Dale, <a href="/A109406/b109406.txt">Table of n, a(n) for n = 1..1000</a>
%e A109406 3 is OK because (sp(3)+sp(4)+sp(5))/3=(9+10+14)/3 = 11; sp(n) = n-th semiprime.
%t A109406 Flatten[Position[Partition[Select[Range[600],PrimeOmega[#]==2&],3,1], _?( IntegerQ[ Total[#]/3]&),{1},Heads->False]] (* _Harvey P. Dale_, Jan 23 2016 *)
%o A109406 (PARI) lista(nn) = {vec = vector(nn, i, i); sp = select(i->(bigomega(i)==2), vec); for (i = 1, #sp-2, if (((sp[i]+sp[i+1]+sp[i+2]) % 3) == 0, print1(i, ", ")););} \\ _Michel Marcus_, Oct 06 2013
%Y A109406 Cf. A075541.
%K A109406 nonn
%O A109406 1,1
%A A109406 _Zak Seidov_, Jun 27 2005