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A098768 Deficient numbers whose reversal is an abundant number. 3
21, 27, 45, 63, 65, 69, 81, 87, 201, 207, 211, 213, 218, 219, 225, 231, 235, 237, 238, 243, 249, 253, 255, 259, 261, 267, 273, 275, 279, 285, 291, 293, 297, 299, 401, 403, 405, 407, 411, 417, 422, 423, 429, 435, 441, 445, 446, 447, 453, 459, 463, 465, 471 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Harvey P. Dale)

EXAMPLE

a(1) = 21 because 21 is a deficient number whose reversal, 12, is an abundant number.

MATHEMATICA

dnanQ[n_]:=Module[{rev=FromDigits[Reverse[IntegerDigits[n]]]}, DivisorSigma[ 1, n]<2n&&DivisorSigma[1, rev]>2rev]; Select[Range[500], dnanQ] (* Harvey P. Dale, Apr 06 2013 *)

CROSSREFS

Cf. A004086, A005100, A005101, A098770.

Sequence in context: A072392 A144415 A098898 * A208157 A114168 A103083

Adjacent sequences:  A098765 A098766 A098767 * A098769 A098770 A098771

KEYWORD

easy,nonn,base

AUTHOR

Shyam Sunder Gupta, Oct 02 2004

STATUS

approved

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Last modified April 21 19:16 EDT 2021. Contains 343156 sequences. (Running on oeis4.)