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A329660
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Numbers m such that sigma(m) is a Lucas number (A000032), where sigma(m) is the sum of divisors of m (A000203).
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1
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1, 2, 3, 4, 10, 17, 688, 1075, 103681, 7860997, 10749957121, 115561578124838522881, 488296733939737583689, 489501979450313254561, 3628116960730713370000, 8784132317383836036997, 8784200214538920269317, 50755107290462736080376601, 94426187701102977738552612783157
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OFFSET
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1,2
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COMMENTS
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Prime numbers of the form L(k)-1, where L(k) is the k-th Lucas number, are in this sequence. The terms 2, 3, 17, 103681, and 10749957121 are primes of this form (with k = 2, 3, 6, 24, 48). Also in the sequence is the prime L(96) - 1 = 115561578124838522881.
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LINKS
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EXAMPLE
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4 is in the sequence since sigma(4) = 7 is a Lucas number.
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MATHEMATICA
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f = LucasL @ Range[1, 40]; Select[Range[10^6], MemberQ[f, DivisorSigma[1, #]] &] (* after Giovanni Resta at A272412 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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