A068675 Numbers k such that a prime can be obtained by inserting a 1 before, somewhere inside, or after the digits of k.

1, 3, 4, 6, 7, 9, 10, 13, 15, 18, 19, 21, 24, 25, 27, 28, 31, 33, 37, 39, 40, 42, 43, 46, 49, 51, 52, 54, 57, 60, 63, 64, 66, 67, 69, 70, 73, 75, 76, 79, 81, 82, 88, 91, 93, 94, 97, 99, 102, 103, 105, 106, 109, 115, 117, 118, 120, 123, 127, 129, 130, 132, 136, 138, 139

Offset

1,2

Links

Table of n, a(n) for n=1..65.

Mathematica

i1[n_] := FromDigits/@Table[Insert[IntegerDigits[n], 1, k], {k, 1, Length[IntegerDigits[n]]+1}]; Select[Range[140], Or@@PrimeQ/@i1[ # ]&]

Crossrefs

Sequence in context: A187580 A094178 A085795 * A190858 A026315 A143264

Adjacent sequences: A068672 A068673 A068674 * A068676 A068677 A068678

Keyword

base,easy,nonn

Author

Amarnath Murthy, Mar 02 2002

Extensions

More terms from Eli McGowan (ejmcgowa(AT)mail.lakeheadu.ca), May 05 2002

Edited by Dean Hickerson, Jun 17 2002

Status

approved