A120819 Indices of primes in A057137.
171, 277, 367, 561, 567, 18881
Offset: 1
Examples
a(1) = 12345678901234567890...01234567890...012345678901 = A057137(171) is the first prime term in A057137.
References
- Clifford A. Pickover, A Passion for Mathematics, Wiley, 2005; see p. 61, 298.
Crossrefs
Programs
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Mathematica
fQ[n_] := PrimeQ@ FromDigits@ Mod[Range@n, 10]; lst = {}; Do[ If[fQ@n, AppendTo[lst, n]; Print@n], {n, 10000}]; lst IntegerLength[Select[Table[FromDigits[PadRight[{},n,{1,2,3,4,5,6,7,8,9,0}]],{n,1,1001,2}],PrimeQ]] (* Harvey P. Dale, Feb 07 2024 *) -
PARI
N=0;for(n=1,600,if(ispseudoprime(N=10*N+n%10),print1(n", "))) \\ Charles R Greathouse IV, May 10 2014 (Comment: Surprisingly, this is faster than calling ispseudoprime() only when n ends in 1 or 7, even when much larger N's are considered, e.g., up to 3000. - M. F. Hasler, Apr 14 2024)
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Python
from sympy import isprime L = ['8901', '234567']; s = '1234567'; c = len(s); m = 0 while c < 18881: s += L[m%2]; c = len(s); m += 1 if isprime(int(s)): print(c, end = ', ') # Ya-Ping Lu, Jan 24 2025
Extensions
a(6) from Arjen Lenstra, Feb 20 2012
Comments