cp's OEIS Frontend

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.

A077650 Initial decimal digit of sigma(n), the sum of divisors of n.

This page as a plain text file.
%I A077650 #11 Nov 18 2017 09:06:59
%S A077650 1,3,4,7,6,1,8,1,1,1,1,2,1,2,2,3,1,3,2,4,3,3,2,6,3,4,4,5,3,7,3,6,4,5,
%T A077650 4,9,3,6,5,9,4,9,4,8,7,7,4,1,5,9,7,9,5,1,7,1,8,9,6,1,6,9,1,1,8,1,6,1,
%U A077650 9,1,7,1,7,1,1,1,9,1,8,1,1,1,8,2,1,1,1,1,9,2,1,1,1,1,1,2,9,1,1,2,1,2,1,2,1
%N A077650 Initial decimal digit of sigma(n), the sum of divisors of n.
%H A077650 Antti Karttunen, <a href="/A077650/b077650.txt">Table of n, a(n) for n = 1..10000</a>
%H A077650 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%F A077650 a(n) = A000030(A000203(n)).
%t A077650 Table[First[IntegerDigits[DivisorSigma[1, w]]], {w, 1, 128}]
%o A077650 (PARI) a(n) = digits(sigma(n))[1]; \\ _Michel Marcus_, Nov 18 2017
%Y A077650 Cf. A000030, A000203, A067342.
%K A077650 base,nonn
%O A077650 1,2
%A A077650 _Labos Elemer_, Nov 19 2002