A167218 Primes whose reversal - 1 is a square.

2, 5, 71, 73, 101, 109, 263, 269, 523, 541, 587, 1061, 1063, 2089, 2251, 2273, 2297, 2843, 2861, 5441, 5477, 5483, 6203, 6221, 7129, 7507, 7937, 10009, 10163, 10169, 10487, 10691, 20201, 20693, 22391, 22769, 24023, 24877, 26141, 26171, 26723

Offset

1,1

Comments

The first digit of a(n) cannot be 3, 4, 8 or 9. - Altug Alkan, Dec 20 2015

Links

Chai Wah Wu, Table of n, a(n) for n = 1..7256

Example

71 is prime and 17-1 = 16 = 4^2.

Prog

(Python)
from sympy import isprime
A167218_list, i, j = [], 0, 1
while j < 10**10:
    p = int(str(j)[::-1])
    if j % 10 and isprime(p):
        A167218_list.append(p)
    j += 2*i+1
    i += 1
A167218_list = sorted(A167218_list) # Chai Wah Wu, Dec 20 2015
(PARI) lista(nn) = {forprime(p=2, nn, if (issquare(eval(concat(Vecrev(Str(p))))-1), print1(p, ", ")); ); } \\ Michel Marcus, Dec 20 2015

Crossrefs

Cf. A007488.

Sequence in context: A066933 A132496 A100009 * A013045 A290864 A309366

Adjacent sequences: A167215 A167216 A167217 * A167219 A167220 A167221

Keyword

base,nonn

Author

Claudio Meller, Oct 30 2009

Status

approved