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A225115 Triangular numbers of the form p^k - 1, where p is a prime number and k >= 2. 1
3, 15, 120, 528, 4095, 139128, 160554240, 812293020528, 379188080252621270252095320 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

There are at least other 4 terms greater than a(9) that can be easily obtained by solving the Diophantine equation T(n) = p^2-1, the smallest being T(75055187665070250755513356704300447). - Giovanni Resta, Apr 29 2013

LINKS

Table of n, a(n) for n=1..9.

PROG

(PARI) t=0; for(n=1, 10^9, t+=n; if(isprimepower(t+1)>=2, print1(t, ", "))); \\ Joerg Arndt, Apr 29 2013

CROSSREFS

Cf. A006454, A025475.

Sequence in context: A068052 A068859 A006454 * A303353 A112228 A260511

Adjacent sequences:  A225112 A225113 A225114 * A225116 A225117 A225118

KEYWORD

nonn,hard,more

AUTHOR

Alex Ratushnyak, Apr 29 2013

EXTENSIONS

a(9) from Giovanni Resta, Apr 29 2013

STATUS

approved

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Last modified November 11 22:31 EST 2019. Contains 329046 sequences. (Running on oeis4.)