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A272650 Sum_{ i in 1..p-1, j in 1..p-1, i*j mod p = 1} i*j, where p = n-th prime. 1
1, 5, 29, 83, 351, 519, 1291, 1747, 3357, 6553, 7501, 11839, 17219, 19263, 28199, 38583, 56049, 49043, 74771, 96133, 89059, 132087, 155209, 185653, 221741, 260983, 274803, 331913, 314355, 348943, 482091, 569587, 641707 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

Tsz Ho Chan, Product of a number and its multiplicative inverse, moments of L-functions and exponential sums, Integers, 16 (2016), #A2.

LINKS

Gheorghe Coserea, Table of n, a(n) for n = 1..20000

MAPLE

f:=proc(n) local p, a, b, s;

p:=ithprime(n); s:=0;

for a from 1 to p-1 do

for b from 1 to p-1 do

if (a*b mod p) = 1 then s:=s+a*b; fi;

od: od:

s; end;

[seq(f(n), n=1..40)];

PROG

(PARI) a(n) = { my(p = prime(n)); sum(i = 1, p-1, i*lift(Mod(i, p)^(-1))); }

vector(33, n, a(n)) \\ Gheorghe Coserea, May 16 2016

CROSSREFS

Sequence in context: A087348 A154412 A236075 * A050409 A111937 A215850

Adjacent sequences:  A272647 A272648 A272649 * A272651 A272652 A272653

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, May 10 2016

STATUS

approved

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Last modified October 15 11:48 EDT 2018. Contains 316229 sequences. (Running on oeis4.)