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A072362
Composite numbers whose sum of aliquot divisors is palindromic.
2
4, 6, 8, 9, 10, 15, 20, 21, 25, 36, 38, 45, 49, 54, 82, 87, 150, 189, 195, 219, 230, 243, 247, 248, 291, 321, 329, 333, 336, 352, 355, 381, 384, 385, 396, 398, 402, 411, 432, 458, 465, 471, 473, 478, 486, 501, 533, 536, 538, 552, 556, 561, 574, 578, 596, 602
OFFSET
1,1
COMMENTS
The sum of the aliquot divisors of n must be greater than one. - Harvey P. Dale, Aug 12 2012
LINKS
EXAMPLE
a(8) = 21: sum of aliquot divisors of 21 = 1+3+7 = 11, which is a palindrome.
MATHEMATICA
adpQ[n_]:=Module[{sad=Total[Most[Divisors[n]]], idsad}, idsad = IntegerDigits[sad]; sad>1&&idsad==Reverse[idsad]]; Select[Range[ 700], adpQ] (* Harvey P. Dale, Aug 12 2012 *)
Select[Range[1000], CompositeQ[#] && PalindromeQ @ (DivisorSigma[1, #] - #) &] (* Amiram Eldar, Aug 17 2020 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Shyam Sunder Gupta, Jul 18 2002
STATUS
approved