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 A236387 #12 Jan 09 2015 13:11:35 %S A236387 5,6,11,19,20,26,28,29,30,39,40,41,46,51,55,58,71,86,89,99,104,109, %T A236387 114,116,117,125,131,135,158,177,181,201,202,203,209,216,226,236,239, %U A236387 245,271,278,306,336,340,352,377,379,398,410,411,419,428,442,447,461 %N A236387 Numbers n such that sigma(n) is an oblong number. %C A236387 An oblong number (A002378) is of the form k(k+1) where k is a natural number. %C A236387 The subsequence of prime terms is A002327 (primes of form n^2 - n - 1). - _Michel Marcus_, Jan 09 2015 %H A236387 Giovanni Resta, <a href="/A236387/b236387.txt">Table of n, a(n) for n = 1..10000</a> %e A236387 sigma(40) = 90 = 9*10, an oblong number; so 40 is a term of the sequence. %t A236387 Select[Range[500], IntegerQ@ Sqrt[1+4*DivisorSigma[1, #]] &] (* _Giovanni Resta_, Jan 24 2014 *) %Y A236387 Cf. A000203, A002327, A002378. %K A236387 nonn,easy %O A236387 1,1 %A A236387 _Joseph L. Pe_, Jan 24 2014 %E A236387 a(12)-a(56) from _Giovanni Resta_, Jan 24 2014