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 A032662 #15 Sep 05 2024 17:10:23 %S A032662 1,2,1,4,3,12,1,2,1,2,3,6,1,6,3,4,5,4,5,8,7,2,21,10,17,2,1,2,3,4,1,2, %T A032662 7,14,3,4,1,2,1,2,11,6,5,18,3,4,3,6,1,2,1,8,5,4,7,2,1,4,5,4,11,2,1,4, %U A032662 3,12,1,2,9,2,3,6,1,8,9,2,3,6,1,2,1,2,5,4,929,6,3,4,5,12,1,2,1 %N A032662 a(n) is the least k such that k concatenated with k + n is prime. %C A032662 First terms of sequences '1', A030457, A032617-A032624, continued with displacements d > 9. %H A032662 Robert Israel, <a href="/A032662/b032662.txt">Table of n, a(n) for n = 0..10000</a> %e A032662 a(22) = 21: the concatenation of 21 and 21 + 22 = 43 is 2143 and this is a prime. %p A032662 tcat:= (a,b) -> a*10^(1+ilog10(b))+b: %p A032662 f:= proc(n) local k; %p A032662 for k from 1 + (n mod 2) by 2 do %p A032662 if isprime(tcat(k,k+n)) then return k fi %p A032662 od; %p A032662 end proc: %p A032662 map(f, [$0..100]); # _Robert Israel_, Sep 05 2024 %Y A032662 Cf. A032663. %K A032662 nonn,base,look %O A032662 0,2 %A A032662 _Patrick De Geest_, May 15 1998 %E A032662 Edited by _Robert Israel_, Sep 05 2024