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A076170 Triangular numbers whose largest proper divisor is also triangular. 1
1, 3, 6, 45, 210, 7140, 122265, 242556, 1702935, 8239770, 279909630, 4601330415, 9508687656, 64088265153, 323015470680, 10973017315470, 173166468725253, 372759573255306, 2411897769074475, 12662852473364940, 430164224521152660, 6516946879404850395 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
No more terms < 10^16. - David Wasserman, Apr 05 2005
2^63 < a(23) <= 14612920781245825506. - Donovan Johnson, Apr 24 2011
LINKS
PROG
(PARI) isTriang(n) = local(x); x = sqrtint(2*n); n == x*(x + 1)/2;
i = 1; n = 1; print1(n, ", "); while(1, i++; n += i; f = factor(n); if (isTriang(n/f[1, 1]), print1(n, ", "))); \\ David Wasserman, Apr 05 2005
CROSSREFS
Sequence in context: A009581 A088674 A203434 * A137775 A038050 A194080
KEYWORD
nonn
AUTHOR
Jason Earls, Nov 01 2002
EXTENSIONS
More terms from David Wasserman, Apr 05 2005
a(20)-a(22) from Donovan Johnson, Apr 24 2011
STATUS
approved

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Last modified May 26 08:09 EDT 2024. Contains 372807 sequences. (Running on oeis4.)