

A287959


Odd primes p such that p^2 divides A001205(p)(p1)/2.


0




OFFSET

1,1


COMMENTS

Carlitz proved that A001205(p) == (p1)/2 (mod p) for all odd primes p. This sequence consists of odd primes for which A001205(p) == (p1)/2 (mod p^2) holds.
a(7) > 2.3*10^7.  Giovanni Resta, Jun 04 2017


LINKS

Table of n, a(n) for n=1..6.
Leonard Carlitz, Congruences for the Number of nGons Formed by n Lines, The American Mathematical Monthly, Vol. 61, No. 6 (1954), pp. 407411.


MATHEMATICA

a[1] = 0; a[2] = 0; a[3] = 1; a[n_] := a[n] = (n  1)*(a[n  1] + (n  2)*a[n  3]/2); lst = {}; k = 3; While[Length[lst] < 5, If[PrimeQ[k] && Divisible[a[k]  (k  1)/2, k^2], lst = AppendTo[lst, k]]; k++]; lst


CROSSREFS

Cf. A001205.
Sequence in context: A290777 A309401 A190637 * A326970 A076361 A130408
Adjacent sequences: A287956 A287957 A287958 * A287960 A287961 A287962


KEYWORD

nonn,more


AUTHOR

Amiram Eldar, Jun 03 2017


EXTENSIONS

a(6) from Giovanni Resta, Jun 04 2017


STATUS

approved



