A053198 -id:A053198

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Search: a053198 -id:a053198

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A280187

Numbers n such that 2 * (1^n + 2^n + 3^n + ... + n^n) is not 0 (mod n), but 2 * (1^d + 2^d + 3^d + ... + d^d) is 0 (mod d) for each other d | n.

+10
2

6, 20, 110, 272, 506, 812, 2162, 2756, 3422, 4970, 6806, 7832, 11342, 12656, 17030, 18632, 22052, 27722, 29756, 31862, 36290, 38612, 51302, 54056, 56882, 62750, 65792, 68906, 72092, 85556, 96410, 100172, 120062, 124256, 128522

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..4000

PROG

(PARI) has(n)=my(f=factor(n)[, 1]); for(i=1, #f, if(n%(f[i]-1)==0 && f[i]>2, return(1))); 0

is(n)=if(n%2, return(0)); if(n%3==0, return(n==6)); if(n%20==0, return(n==20)); if(!has(n), return(0)); my(f=factor(n)[, 1]); for(i=1, #f, if(has(n/f[i]), return(0))); 1 \\ Charles R Greathouse IV, Dec 28 2016

CROSSREFS

Primitive elements of A228870.

Subsequence of A002943. Also a subsequence of A028689, A036689, A053198, A068377, A079143, A128672, A220211 and other sequences ...- Paolo P. Lava, Jan 10 2017

KEYWORD

nonn

AUTHOR

Charles R Greathouse IV, Dec 28 2016

STATUS

approved

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