A272524 Refactorable triangular numbers.

1, 36, 136, 276, 1176, 2016, 2556, 2628, 3240, 4560, 11628, 12720, 12880, 18336, 18528, 25200, 32640, 32896, 51360, 64620, 73920, 86320, 89676, 100128, 114960, 115440, 126756, 131328, 148240, 166176, 248160, 253116, 265356, 270480, 294528, 295296, 320400, 345696, 373680, 380628, 400960, 401856, 438516

Offset

1,2

Comments

Intersection of A000217 and A033950.

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

36 is a term as the number of divisors of 36 (see A000005) is 9 which divides 36.

Mathematica

Select[PolygonalNumber@Range@1000, Divisible[#, DivisorSigma[0, #]]&]

Prog

(PARI) for (n=1, 1000, t=n*(n+1)/2; t%numdiv(t)==0 && print1(t ", " ))

Crossrefs

Cf. A000217 (triangular numbers), A033950 (refactorable numbers), A063440 (number of divisors of triangular numbers), A000005 (number of divisors), A036907 (refactorable squares).

Sequence in context: A044368 A044749 A067865 * A303899 A245530 A138202

Adjacent sequences: A272521 A272522 A272523 * A272525 A272526 A272527

Keyword

nonn

Author

Waldemar Puszkarz, May 01 2016

Status

approved