A228625 Primes of the form abcabc..abca.

1021, 1031, 1051, 1061, 1091, 1151, 1171, 1181, 1201, 1231, 1291, 1301, 1321, 1361, 1381, 1451, 1471, 1481, 1511, 1531, 1571, 1601, 1621, 1721, 1741, 1801, 1811, 1831, 1861, 1871, 1901, 1931, 1951, 3023, 3083, 3163, 3203, 3253, 3313, 3323, 3343, 3373, 3413

Offset

1,1

Comments

The sequence appears to be infinite.

Links

Shyam Sunder Gupta and Charles R Greathouse IV, Table of n, a(n) for n = 1..829 (all terms with up to 1000 digits; first 500 from Gupta)

Example

a(2)= 1031 is in the sequence because it is a prime of the form abca.

Mathematica

s[n_]:=Select[Union@Flatten@Table[FromDigits@Flatten@Join[IntegerDigits@Table[b, {n}], {IntegerDigits@Floor[b/100]}], {b, 100, 999}], PrimeQ]; Array[s, 2]//Flatten

Prog

(PARI) for(k=1, 9, b=10^(3*k+1); for(n=1, 999, if(isprime(t=b*n\999), print1(t", ")))) \\ Charles R Greathouse IV, Aug 29 2013

Crossrefs

Sequence in context: A167846 A303918 A371378 * A356947 A214732 A088290

Adjacent sequences: A228622 A228623 A228624 * A228626 A228627 A228628

Keyword

nonn,base

Author

Shyam Sunder Gupta, Aug 28 2013

Status

approved