A351220 Numbers k such that sigma(L(k)) > 2*L(K), where L(k) is the k-th Lucas number.
6, 18, 30, 42, 45, 54, 66, 75, 78, 90, 102, 105, 114, 126, 135, 138, 150, 162, 165, 174, 186, 195, 198, 210, 222, 225, 234, 246, 258, 270, 282, 294, 306, 315, 318, 330, 342, 354, 366, 375, 378, 390, 402, 405, 414, 426, 435, 438, 450, 462, 474, 486, 495, 498, 510
Offset: 1
Keywords
Links
- Amiram Eldar, Table of n, a(n) for n = 1..142
- Charles R. Wall, Problem H-338, Advanced Problems and Solutions, The Fibonacci Quarterly, Vol. 20, No. 1 (1982), p. 94; Some Abundance, Solution to Problem H-338 by the proposer, ibid., Vol. 21, No. 2 (1983), pp. 159-160.
Programs
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Mathematica
Select[Range[0, 250], DivisorSigma[-1, LucasL[#]] > 2 &]
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Python
from sympy import divisor_sigma, lucas print([k for k in range(150) if divisor_sigma(lucas(k)) > 2*lucas(k)]) # Karl-Heinz Hofmann, Feb 07 2022
Comments