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 A072668 #29 Aug 02 2024 12:04:38 %S A072668 3,5,7,8,9,11,13,14,15,17,19,20,21,23,24,25,26,27,29,31,32,33,34,35, %T A072668 37,38,39,41,43,44,45,47,48,49,50,51,53,54,55,56,57,59,61,62,63,64,65, %U A072668 67,68,69,71,73,74,75,76,77,79,80,81,83,84,85,86,87,89,90,91,92,93,94,95 %N A072668 Numbers one less than composite numbers. %C A072668 Complement of A006093 (primes minus 1). %C A072668 Numbers which can be written as i*j+i+j, 0<i<=j: A072670(a(n))>0 for n>1. %C A072668 a(n)! is divisible by a(n)*(a(n)+1)/2, see A060462. %H A072668 Michael De Vlieger, <a href="/A072668/b072668.txt">Table of n, a(n) for n = 1..10000</a> %F A072668 a(n) = A002808(n) - 1. %F A072668 a(n) = 2*A002808(n) - A079696(n). - _Juri-Stepan Gerasimov_, Oct 22 2009 %F A072668 a(n) = A060462(n). %t A072668 Select[Range[4, 96], CompositeQ] - 1 (* _Michael De Vlieger_, Dec 10 2020 *) %o A072668 (PARI) for(n=2,100,if(!isprime(n),print1(n-1,", "))) \\ _Derek Orr_, Jun 08 2015 %o A072668 (Magma) [n-1: n in [2..120] | not IsPrime(n)]; // _Vincenzo Librandi_, Jun 09 2015 %o A072668 (Python) %o A072668 from sympy import composite %o A072668 def A072668(n): return composite(n)-1 # _Chai Wah Wu_, Aug 02 2024 %Y A072668 Cf. A060462, A066938, A072672. %Y A072668 Cf. A002808, A006093, A079696. %K A072668 nonn,easy %O A072668 1,1 %A A072668 _Henry Bottomley_, Apr 11 2001