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 A103398 #23 Sep 01 2024 02:29:17
%S A103398 4,9,15,21,33,38,58,65,86,106,121,129,265,511,2047,2049,4109,16293,
%T A103398 16489,17855,19857,32678,34709,66217,104739,220918,240367,262298,
%U A103398 293323,954413,2082999,3145729,3498467,4296813,16442015,18037939,21317326
%N A103398 Semiprimes in A103378.
%F A103398 Intersection of A103378 with A001358.
%p A103398 A103378 := proc(n) option remember; if n <= 11 then 1 ; else procname(n-10)+procname(n-11) ; fi ; end proc:
%p A103398 a78prev := -1 ; for n from 1 to 400 do a78 := A103378(n) ; if numtheory[bigomega](a78) = 2 and a78 <> a78prev then printf("%d,",a78) ; end if; a78prev := a78 ; end do: # _R. J. Mathar_, Jun 11 2010
%t A103398 SemiprimeQ[n_]:=Plus@@FactorInteger[n][[All, 2]]?2; Clear[a]; k=10; Do[a[n]=1, {n, k+1}]; a[n_]:=a[n]=a[n-k]+a[n-k-1]; A103377=Array[a, 100] A103387=Union[Select[Array[a, 1000], PrimeQ]] A103397=Union[Select[Array[a, 300], SemiprimeQ]] N[Solve[x^11 - x - 1 == 0, x], 111][[2]] (* _Ray Chandler_ and _Robert G. Wilson v_ *)
%Y A103398 Cf. A001358, A103378, A103388.
%K A103398 easy,nonn
%O A103398 1,1
%A A103398 _Jonathan Vos Post_, Feb 15 2005
%E A103398 Edited and extended by _Ray Chandler_ and _Robert G. Wilson v_
%E A103398 Entries >511 corrected by _R. J. Mathar_, Jun 11 2010