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A243008 Triangular numbers divisible by the square of the sum of their digits. 1
1, 10, 3240, 3321, 13041, 13203, 15400, 65341, 80200, 90100, 161028, 210276, 260281, 265356, 266085, 300700, 346528, 500500, 937765, 947376, 1043290, 1228528, 1313010, 1628110, 2049300, 2390391, 2421100, 3357936, 3746953, 4020030, 5250420, 6641190, 6857956, 6939675 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Intersection of A000217 and A072081.

LINKS

K. D. Bajpai, Table of n, a(n) for n = 1..12445

EXAMPLE

a(3) = 3240 = 80 * (80 + 1)/2 is a triangular number. Since 3240 is divisible by (3 + 2 + 4 + 0)^2 = 81, it appears in the sequence.

a(3) = 3321 = 81 * (81 + 1)/2 is a triangular number. Since 3321 is divisible by (3 + 3 + 2 + 1)^2 = 81, it appears in the sequence.

MATHEMATICA

Select[Table[n*(n + 1)/2, {n, 10000}], Divisible[#, Plus @@ IntegerDigits[#]^2] &]

PROG

(PARI)

for(n=1, 10^4, s=n*(n+1)/2; if(s%(sumdigits(s)^2)==0, print1(s, ", "))) \\ Derek Orr, Aug 23 2014

CROSSREFS

Cf. A000217, A072081, A076713, A118693.

Sequence in context: A305666 A320307 A225764 * A133198 A292443 A001329

Adjacent sequences:  A243005 A243006 A243007 * A243009 A243010 A243011

KEYWORD

nonn,base

AUTHOR

K. D. Bajpai, Aug 20 2014

STATUS

approved

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Last modified February 20 04:38 EST 2020. Contains 332063 sequences. (Running on oeis4.)