A395014 Abundant numbers k for which the k-th Fibonacci number is deficient.

20, 56, 66, 70, 78, 88, 100, 102, 104, 112, 114, 138, 174, 176, 186, 196, 208, 220, 222, 224, 246, 258, 260, 272, 282, 304, 308, 318, 340, 350, 352, 354, 364, 366, 368, 380, 392, 402, 416, 426, 438, 448, 460, 464, 474, 476, 490, 498, 500, 532, 534, 544, 550

Offset

1,1

Links

Sean A. Irvine, Table of n, a(n) for n = 1..278 (terms 1..137 from Shyam Sunder Gupta)

Example

a(1) = 20 is a term because 20 is an abundant number as the sum of the aliquot divisors of 20, i.e., 1 + 2 + 4 + 5 + 10 = 22, is more than 20, and 20th Fibonacci number; i.e., 6765 is a deficient number.

Mathematica

A395014Q[k_] := DivisorSigma[1, k] > 2*k && (DivisorSigma[1, #] < 2*# & [Fibonacci[k]]);
Select[Range[500], A395014Q] (* Paolo Xausa, Apr 15 2026 *)

Prog

(PARI) isok(k) = if (sigma(k) > 2*k, my(f=fibonacci(k)); sigma(f) < 2*f); \\ Michel Marcus, Apr 10 2026

Crossrefs

Cf. A000045, A005100, A005101, A074316, A074317, A395013.

Sequence in context: A108108 A316935 A123456 * A144521 A044122 A044503

Adjacent sequences: A395011 A395012 A395013 * A395015 A395016 A395017

Keyword

nonn

Author

Shyam Sunder Gupta, Apr 10 2026

Status

approved