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 A039928 #18 Dec 25 2022 19:57:53 %S A039928 0,3,3,0,10,12,1,24,25,32,116,12,412,109,126,2389,12497,28772,126, %T A039928 72795,247786,770213,159378001963452599318,2169128,442,311,378,789, %U A039928 10015050,75,74253544,7881195,2461717833658872781238383813854943728,51,17,824,855,2,29981,3087,215308,123456790123456790123456790123456790123452,132813776,1086162642,1836311902,400276874544 %N A039928 Sum of first n terms of A_n (using absolute values of terms). %C A039928 Since the sequences in the OEIS occasionally change their initial terms (for editorial reasons), this is an especially ill-defined sequence! - _N. J. A. Sloane_, Jan 01 2005 %C A039928 The next term, a(47), is currently unknown. - _Jianing Song_, Oct 07 2018 %H A039928 <a href="/index/Se#selfies">Index entries for sequences whose definition involves A_n (or An)</a>. %e A039928 A000001 (Number of groups of order n) begins 0,... -> a(1) = 0 %e A039928 A000002 (Kolakoski sequence) begins 1, 2,... -> a(2) = 3 %e A039928 A000003 begins 1, 1, 1,... -> a(3) = 3 %e A039928 A000004 (The zero sequence) begins 0, 0, 0, 0,... -> a(4) = 0 %e A039928 A000005 (The number of divisors) begins 1, 2, 2, 3, 2, ... -> a(5) = 10 %e A039928 ... %e A039928 A000010 (Euler totient function) begins 1, 1, 2, 2, 4, 2, 6, 4, 6, ... so a(10) = 1 + 1 + 2 + 2 + 4 + 2 + 6 + 4 + 6 + 4 = 32. %Y A039928 Cf. A031135, A031214, A100543 (uses signed values). %K A039928 dumb,easy,nonn %O A039928 1,2 %A A039928 _Russ Cox_ %E A039928 Corrected and extended by C. Ronaldo (aga_new_ac(AT)hotmail.com), Dec 27 2004 %E A039928 a(1) changed from 1 to 0 and extended by _Jianing Song_, Oct 06 2018