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 A067531 #18 Jul 02 2025 16:02:01 %S A067531 5,6,7,13,15,16,19,21,27,31,33,35,43,51,57,61,65,73,77,87,93,103,105, %T A067531 109,111,135,139,141,143,151,155,161,165,177,181,183,185,189,193,199, %U A067531 201,203,215,229,231,237,241,245,267,271,275,283,285,287,313,321,335 %N A067531 Numbers n such that n - number of divisors of n is a prime. %C A067531 Larger of the twin primes (A006512) is a term. %H A067531 Harvey P. Dale, <a href="/A067531/b067531.txt">Table of n, a(n) for n = 1..1000</a> %e A067531 51 is a term as d(51) = 4 and 51-4 = 47 is a prime. %p A067531 with(numtheory): for n from 3 to 500 do if isprime(n-tau(n)) then printf(`%d,`,n) fi:od: # _James Sellers_, Feb 18 2002 %t A067531 Select[Range[400],PrimeQ[#-DivisorSigma[0,#]]&] (* _Harvey P. Dale_, May 22 2013 *) %Y A067531 Cf. A000005 (number of divisors of n), A006512. %K A067531 easy,nonn %O A067531 1,1 %A A067531 _Amarnath Murthy_, Feb 17 2002 %E A067531 More terms from _James Sellers_, Feb 18 2002