A226108 Primes remaining prime if all but two digits are deleted

11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 113, 131, 137, 173, 179, 197, 311, 317, 431, 617, 719, 1117, 1171, 4111, 11113, 11117, 11119, 11131, 11171, 11173, 11197, 11311, 11317, 11719, 11731, 13171, 13711, 41113

Offset

1,1

Comments

Subsequence of A069488.

References

C. Caldwell, Truncatable primes, J. Recreational Math., 19:1 (1987) 30-33.

Links

Tim Cieplowski, Table of n, a(n) for n = 1..2720

P. Ballew, Knockout Primes and a new notation, May 17, 2013

C. Caldwell, The Prime Glossary: Deletable Prime

Example

For a(3)=137, all pairs of two digits (in their original order) 13, 17, and 37 are prime.

Mathematica

testQ[n_] := n > 9 && Catch[Block[{d = IntegerDigits@n}, Do[If[! PrimeQ[ d[[j]] + 10*d[[i]]], Throw@False], {j, 2, Length@d}, {i, j-1}]; True]]; Select[Prime@ Range[10^5], testQ] (* Giovanni Resta, May 28 2013 *)

Crossrefs

Cf. A019546, A051362, A069488.

Sequence in context: A008364 A140461 A120533 * A273906 A095862 A125845

Adjacent sequences: A226105 A226106 A226107 * A226109 A226110 A226111

Keyword

nonn,base

Author

Tim Cieplowski, May 26 2013

Status

approved