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 A025706 #9 Jul 06 2025 13:07:25 %S A025706 1,3,6,10,15,21,28,37,47,58,70,83,97,113,130,148,167,187,208,231,255, %T A025706 280,306,333,361,391,422,454,487,521,556,592,630,669,709,750,792,835, %U A025706 880,926,973,1021,1070,1120,1172,1225,1279,1334,1390,1447,1506,1566,1627,1689 %N A025706 Index of 5^n within sequence of numbers of form 4^i*5^j. %C A025706 Positions of zeros in A025646. - _R. J. Mathar_, Jul 06 2025 %H A025706 Charles R Greathouse IV, <a href="/A025706/b025706.txt">Table of n, a(n) for n = 0..10000</a> %o A025706 (PARI) a(n)=my(N=1); n+1+sum(i=1, n, logint(N*=5, 4)); \\ _Charles R Greathouse IV_, Jan 11 2018 %o A025706 (PARI) first(n)=my(s, N=1/5); vector(n+1, i, s+=logint(N*=5, 4)+1) \\ _Charles R Greathouse IV_, Jan 11 2018 %Y A025706 Cf. A025646. Differs from A025730 at a(56). %K A025706 nonn,easy %O A025706 0,2 %A A025706 _David W. Wilson_ %E A025706 Offset corrected by _Charles R Greathouse IV_, Jan 11 2018