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A074315 Abundant triangular numbers. 1
36, 66, 78, 120, 210, 276, 300, 378, 528, 630, 666, 780, 820, 990, 1128, 1176, 1326, 1540, 1596, 1770, 1830, 2016, 2080, 2346, 2556, 2628, 2850, 3160, 3240, 3486, 3570, 3828, 4095, 4278, 4560, 4656, 4950, 5460, 5778, 5886, 6216, 6328, 6786, 7140, 7260 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

FORMULA

Intersection of A000217 and A005101. - Michel Marcus, Mar 10 2013

EXAMPLE

a(2)=66 because sum of aliquot divisors of 66 (which is a triangular number) is 1+2+3+6+11+22+33=78 which is more than 66, hence it is abundant. 66 is 2nd abundant triangular number.

MATHEMATICA

Select[Accumulate[Range[150]], Total[Divisors[#]]>2#&] (* Harvey P. Dale, Dec 18 2014 *)

PROG

(PARI) listA074315(m) = {for (i=1, m, t = i*(i+1)/2; if (sigma(t) > 2*t, print1(t, ", ")); ); } \\ up to the m-th triangular number; Michel Marcus, Mar 10 2013

CROSSREFS

Sequence in context: A272190 A060671 A269499 * A240520 A126789 A176623

Adjacent sequences:  A074312 A074313 A074314 * A074316 A074317 A074318

KEYWORD

base,nonn

AUTHOR

Shyam Sunder Gupta, Sep 22 2002

STATUS

approved

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Last modified September 23 22:32 EDT 2020. Contains 337315 sequences. (Running on oeis4.)