[seqfan] n-Wall-Sun-Sun primes

Felix Fröhlich felix.froe at gmail.com
Mon Apr 18 13:06:35 CEST 2016


Dear Sequence fans,

I just started the draft A271782, which gives the smallest n-Wall-Sun-Sun
prime. I did not come up this definition myself, but took it from the
Wikipedia article on Wall-Sun-Sun primes. However, I have some difficulties
understanding the definition of the sequence. In particular, the section on
k-Wall-Sun-Sun primes gives two definitions that are apparently equivalent.
The second definition seems to say that a prime p is a k-Wall-Sun-Sun prime
if V_k(p) == 1 (mod p^2), i.e., p^2 divides V_k(k, -1) if I understand the
page on Lucas sequences in the OEIS Wiki correctly.

Is that correct? Also, it would be nice if someone could confirm the terms
with a program. I don't have PARI code for V_n(P, Q) at the moment,
although this seems relatively easy to implement (I guess one does this
recursively with a function taking three arguments n, P, Q).

Best regards
Felix



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