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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
OFFSET
1,2
COMMENTS
Intersection of A000217 and A072081.
LINKS
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
KEYWORD
nonn,base
AUTHOR
K. D. Bajpai, Aug 20 2014
STATUS
approved