A072125 Concatenation of first n entries (digits) of A007376 is not divisible by 3.

1, 4, 7, 10, 11, 12, 14, 16, 17, 18, 20, 22, 23, 24, 26, 28, 29, 32, 34, 35, 38, 40, 41, 44, 46, 47, 53, 54, 59, 60, 65, 66, 70, 71, 72, 74, 76, 77, 78, 80, 82, 83, 84, 86, 88, 89, 92, 94, 95, 98, 100, 101, 104, 106, 107, 113, 114, 119, 120, 125, 126, 130, 131, 132, 134

Offset

1,2

Comments

Concatenation of some permutations of the n digits of A007376 is likely to be prime.

Links

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

Example

16 is in the sequence because the 16-digit number 1234567891011121 = 1 (mod 3).

Mathematica

f[0] = 0; f[n_Integer] := 10^(Floor[Log[10, n]] + 1)*f[n - 1] + n; Select[ Range[140], Mod[ FromDigits[ Take[ IntegerDigits[ f[n]], n]], 3] != 0 &]

Crossrefs

Cf. A007376 & A033307.

Sequence in context: A093465 A123869 A309688 * A370759 A223024 A275340

Adjacent sequences: A072122 A072123 A072124 * A072126 A072127 A072128

Keyword

easy,nonn,base

Author

Lekraj Beedassy, Jun 20 2002

Extensions

Edited by Robert G. Wilson v, Jun 21 2002

Status

approved