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 A088834 Numbers k such that sigma(k) == 6 (mod k). 7
 1, 5, 6, 25, 180, 8925, 32445, 442365 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS For each integer j in A059609, 2^(j-1)*(2^j - 7) is in the sequence. E.g., for j = A059609(1) = 39 we get 151115727449904501489664. - M. F. Hasler and Farideh Firoozbakht, Dec 03 2013 No more terms to 10^10. - Charles R Greathouse IV, Dec 05 2013 a(9) > 10^13. - Giovanni Resta, Apr 02 2014 a(9) > 1.5*10^14. - Jud McCranie, Jun 02 2019 LINKS Farideh Firoozbakht and M. F. Hasler, Variations on Euclid's formula for perfect numbers, Journal of Integer Sequences 13 (2010), 18 pp. Article ID 10.3.1. EXAMPLE Sigma(25) = 31 = 1*25 + 6, so 31 mod 25 = 6. MATHEMATICA Select[Range[1000000], Mod[DivisorSigma[1, #] - 6, #] == 0 &] (* T. D. Noe, Dec 03 2013 *) PROG (PARI) is(n)=sigma(n)%n==6 \\ Charles R Greathouse IV, Dec 03 2013 CROSSREFS Cf. A054024, A045768, A045769, A045770, A077374, A076496, A087167, A088012. Sequence in context: A038248 A046831 A003226 * A137081 A137079 A163658 Adjacent sequences:  A088831 A088832 A088833 * A088835 A088836 A088837 KEYWORD nonn,more AUTHOR Labos Elemer, Oct 29 2003 EXTENSIONS Terms corrected by Charles R Greathouse IV and Farideh Firoozbakht, Dec 03 2013 STATUS approved

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Last modified August 3 08:21 EDT 2021. Contains 346435 sequences. (Running on oeis4.)