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A072815 Sum of proper divisors of 6n + 1. 1
0, 1, 1, 1, 6, 1, 1, 1, 8, 17, 1, 1, 1, 1, 23, 21, 1, 1, 1, 29, 12, 1, 27, 1, 35, 1, 1, 1, 14, 73, 1, 29, 1, 1, 47, 1, 39, 1, 1, 53, 1, 33, 35, 45, 59, 1, 1, 1, 18, 65, 51, 1, 1, 41, 109, 1, 1, 57, 1, 77, 20, 1, 1, 1, 191, 41, 1, 45, 1, 89, 1, 69, 1, 1, 95, 53, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

the square root of t(n) < s(t(4n-1, 4n-2, 4n-3, 4n-4)) < s(t(4n)).

LINKS

T. D. Noe, Table of n, a(n) for n = 0..1000

Eric Weisstein's World of Mathematics, Perfect Numbers

FORMULA

s(t(n)), where t(n)=6n + 1 and s(n) is the restricted divisor function.

EXAMPLE

a(1) = s(t(1))=1 since t(1)=7 and s(7)=1 under the definition of the restricted divisor function.

MATHEMATICA

Table[c=6n+1; DivisorSigma[1, c]-c, {n, 0, 80}] (* Harvey P. Dale, Nov 13 2013 *)

CROSSREFS

Sequence in context: A034460 A063919 A308135 * A348979 A080304 A340677

Adjacent sequences:  A072812 A072813 A072814 * A072816 A072817 A072818

KEYWORD

nonn

AUTHOR

Hisanobu Shinya (ilikemathematics(AT)hotmail.com), Jul 14 2002

EXTENSIONS

Corrected by Harvey P. Dale, Nov 13 2013

STATUS

approved

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Last modified May 27 08:10 EDT 2022. Contains 354094 sequences. (Running on oeis4.)