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.

A172508 Prime numbers such that the differences between any pair of digits is prime.

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%I A172508 #12 Jan 22 2019 02:48:48
%S A172508 2,3,5,7,13,29,31,41,47,53,61,79,83,97,163,257,461,479,503,613,631,
%T A172508 641,683,853,863,947,2749,4297,4729
%N A172508 Prime numbers such that the differences between any pair of digits is prime.
%C A172508 No further term between 4729 and 7368787 = A000040(500000). - _R. J. Mathar_, Feb 16 2010
%C A172508 As _Robert G. Wilson v_ points out, there are only 4 different single-digit primes, 2, 3, 5 and 7. Therefore the difference between any pair of a term cannot be zero; the terms can only have a maximum of 5 different digits. A full search covering this range shows that the sequence terminates with the 4729. - _R. J. Mathar_, Feb 25 2010
%p A172508 isA172508 := proc(n) local res,dgs,k,l ; dgs := convert(n,base,10) ; if nops(dgs) < 2 or not isprime(n) then return false; else for k from 1 to nops(dgs)-1 do for l from k+1 to nops(dgs) do if not isprime(abs( op(k,dgs)-op(l,dgs) )) then return false; end if; end do ; end do ; end if; return true; end proc: for i from 1 to 500000 do p := ithprime(i) : if isA172508(p) then printf("%d,\n",p) ; end if; end do: # _R. J. Mathar_, Feb 16 2010
%t A172508 Select[Prime[Range[638]],And@@PrimeQ[#[[1]]-#[[2]]&/@ Subsets[ IntegerDigits[ #],{2}]]&] (* _Harvey P. Dale_, Nov 29 2012 *)
%K A172508 nonn,base,fini,full
%O A172508 1,1
%A A172508 _Claudio Meller_, Feb 05 2010
%E A172508 Three more terms from _R. J. Mathar_ and _Robert G. Wilson v_, Feb 16 2010
%E A172508 Edited by _N. J. A. Sloane_, Feb 24 2010
%E A172508 Keywords:fini,full added by _Ray Chandler_ and _R. J. Mathar_, Feb 25 2010