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 A025723 #27 Jul 06 2025 14:40:47
%S A025723 1,3,6,10,15,22,30,39,49,60,73,87,102,118,135,154,174,195,217,240,265,
%T A025723 291,318,346,376,407,439,472,506,542,579,617,656,696,738,781,825,870,
%U A025723 916,964,1013,1063,1114,1166,1220,1275,1331,1388,1447,1507,1568,1630,1693
%N A025723 Index of 7^n within sequence of numbers of form 5^i*7^j.
%C A025723 Positions of zeros in A025652. - _R. J. Mathar_, Jul 06 2025
%H A025723 Robert Israel, <a href="/A025723/b025723.txt">Table of n, a(n) for n = 0..10000</a>
%F A025723 a(n) = 1 + Sum_{k=1..n} ceiling(k*log_5(7)). - _Robert Israel_, Nov 16 2016
%p A025723 ListTools:-PartialSums([1,seq(ceil(k*log[5](7)),k=1..100)]); # _Robert Israel_, Nov 16 2016
%t A025723 Table[1 + Sum[Ceiling[k Log[5, 7]], {k, n}], {n, 0, 52}] (* _Michael De Vlieger_, Nov 16 2016 *)
%o A025723 (PARI) a(n)=my(N=1); n+1+sum(i=1, n, logint(N*=7, 5)); \\ _Charles R Greathouse IV_, Jan 11 2018
%o A025723 (PARI) first(n)=my(s, N=1/7); vector(n+1, i, s+=logint(N*=7, 5)+1) \\ _Charles R Greathouse IV_, Jan 11 2018
%Y A025723 Cf. A025708, A022330, A022331, etc.
%K A025723 nonn,easy
%O A025723 0,2
%A A025723 _David W. Wilson_
%E A025723 Offset changed to 0 by _Robert Israel_, Nov 16 2016