%I #10 Oct 18 2016 09:36:32

%S 1,4,5,8,11,18,23,30,37,42,43,44,57,58,69,80,81,86,93,94,97,100,101,

%T 102,103,108,109,110,111,116,123,124,125,132,133,134,137,140,143,144,

%U 145,146,165,172,175,178,181,186,193,196,197,198,203,204,215,218,219

%N a(1)=1; for n>1, a(n) = least integer > a(n-1) such that a(n)^2-a(n-1)^2 = semiprime

%H Harvey P. Dale, <a href="/A144062/b144062.txt">Table of n, a(n) for n = 1..1000</a>

%e 2^2-1=3, not semiprime; 3^2-1=8, not semiprime; 4^2-1=15=3*5, semiprime, hence a(2)=4.

%t sp[n_]:=Module[{k=n+1},While[PrimeOmega[k^2-n^2]!=2,k++];k]; NestList[ sp,1,60] (* _Harvey P. Dale_, Oct 18 2016 *)

%o (PARI) lista(nn) = {cura = 1; print1(cura, ", "); for (n=1, nn, nexta = cura + 1; while (bigomega(nexta^2-cura^2) != 2, nexta++); cura = nexta; print1(nexta, ", "););} \\ _Michel Marcus_, Feb 28 2014

%Y Cf. A001358.

%K easy,nonn

%O 1,2

%A Philippe Lallouet (philip.lallouet(AT)orange.fr), Sep 09 2008

%E Corrected and extended by _Michel Marcus_, Feb 28 2014