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 A228625 Primes of the form abcabc..abca. 4
 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 (list; graph; refs; listen; history; text; internal format)
 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

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Last modified April 21 01:42 EDT 2024. Contains 371850 sequences. (Running on oeis4.)