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 A173226 #20 Aug 10 2024 13:32:13
%S A173226 1,2,7,68,1453,51974,2754739,202115720,19593627865,2424473303306,
%T A173226 372795661540831,69721670054678732,15584255833611765637,
%U A173226 4102656765126735657998,1256362298168756601126283,442800255547191861154809104,177962191835086481297819598769
%N A173226 Partial sums of A000364.
%C A173226 Partial sums of Euler numbers. Partial sums of secant or "Zig" numbers. The subsequence of prime partial sum of Euler numbers begins 2, 7, 1453, no more through a(17). What is the next such prime?
%F A173226 a(n) = Sum_{i=0..n} A000364(i).
%F A173226 G.f.: 1/U(0)/(1-x) where U(k)=1 + x - x*(2*k+1)*(2*k+2)/(1 - x*(2*k+1)*(2*k+2)/U(k+1)) ; (continued fraction, 2-step). - Sergei N. Gladkovskii, Oct 15 2012
%F A173226 G.f.: 1/(1-x)/Q(0), where Q(k)= 1 - x*(2*k+1)^2/(1 - x*(2*k+2)^2/Q(k+1)); (continued fraction). - _Sergei N. Gladkovskii_, Apr 27 2013
%F A173226 G.f.: Q(0)/(1-x), where Q(k) = 1 - x*(k+1)^2/( x*(k+1)^2 - 1/Q(k+1) ); (continued fraction). - _Sergei N. Gladkovskii_, Oct 22 2013
%t A173226 Accumulate[Table[Abs[EulerE[2n]],{n,0,20}]] (* _Harvey P. Dale_, Aug 10 2024 *)
%o A173226 (Python)
%o A173226 from sympy import euler
%o A173226 def A173226(n): return sum(abs(euler(i)) for i in range(0,(n<<1)+1,2)) # _Chai Wah Wu_, Apr 16 2023
%Y A173226 Cf. A000111, A000364, A000182, A011248, A060075, A013525, A000816, A002436, A028296, A122045.
%K A173226 easy,nonn
%O A173226 0,2
%A A173226 _Jonathan Vos Post_, Feb 13 2010