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A078923 Possible values of sigma(n)-n. 4
0, 1, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

To test whether k>1 is in the sequence, it suffices to check values of n up to (k-1)^2, since sigma(n)-n >= sqrt(n)+1 if n is composite.

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..1000

PROG

(PARI) lista(nn) = {for (n=0, nn, if (n==1, kmax=2, kmax=(n-1)^2); for (k=1, kmax, if (sigma(k)-k == n, print1(n, ", "); break); ); ); } \\ Michel Marcus, Nov 11 2014

CROSSREFS

Cf. A000203, A001065, A002191, A007369. Complement of A005114.

Sequence in context: A317093 A181590 A243293 * A165240 A092460 A092459

Adjacent sequences:  A078920 A078921 A078922 * A078924 A078925 A078926

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Dec 15 2002

EXTENSIONS

Edited by Dean Hickerson, Dec 19 2002

Offset fixed by Michel Marcus, Dec 19 2014

STATUS

approved

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Last modified October 20 17:24 EDT 2018. Contains 316392 sequences. (Running on oeis4.)