A098768 Deficient numbers whose reversal is an abundant number.

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

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