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 A097961 Numbers n such that the sum of the first n odd primes is divisible by n. 1
 1, 2, 3, 60, 73, 357, 690, 970, 1560, 1844, 2016, 2071, 3267, 7034, 22388, 37244, 137166, 808334, 1126996, 3420839, 4971830, 14647946, 15553569, 21957090, 31327140, 90514444, 98576118, 204198604, 210662116, 553825420 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS FORMULA When A071148(n) / n or (A007504(n+1)-2)/n is an integer. EXAMPLE a(1) = 1 since 3 is divisible by 1. a(2) = 2 since 3 + 5 = 8 is divisible by 2. a(3) = 3 since 3 + 5 + 7 = 15 is divisible by 3. a(4) != 4 since 3 + 5 + 7 + 11 = 26 is not divisible by 4. 98576118 * 977748014 = 96382603602329652. MATHEMATICA NextPrim[n_] := Block[{k = n + 1}, While[ !PrimeQ[k], k++ ]; k]; p = 2; s = 0; Do[p = NextPrim[p]; s = s + p; If[ Mod[s, n] == 0, Print[n]], {n, 151666666}] (* Robert G. Wilson v, Oct 23 2004 *) PROG (C++) #include #include using namespace std; int primes[999] = {/* first 999 odd primes here, omitted for space*/}; int total = 0; int main() {   for (int a = 1; a < 1000; a++)  {     total = total + primes[a-1];     if (total % a == 0) cout << a << ", ";   }   return 0; } /* Anne Donovan, Oct 22 2004 */ CROSSREFS Cf. A071148. Sequence in context: A152657 A299172 A154253 * A145556 A124083 A112098 Adjacent sequences:  A097958 A097959 A097960 * A097962 A097963 A097964 KEYWORD easy,nonn AUTHOR Anne M. Donovan (anned3005(AT)aol.com), Oct 22 2004 EXTENSIONS More terms from Robert G. Wilson v, Oct 23 2004 a(28)-a(30) from Rémy Sigrist, Sep 25 2016 STATUS approved

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Last modified June 14 01:29 EDT 2021. Contains 345016 sequences. (Running on oeis4.)