A340861 a(n) is the least prime of the form Sum_{1<=i<=2*n-1} prime(i+1)*prime(i+k)

83, 373, 1543, 2393, 4723, 13997, 18047, 38039, 43777, 62801, 56383, 95803, 109433, 122701, 173687, 268973, 250949, 359441, 363619, 430589, 832331, 813797, 932749, 925273, 1052719, 1356499, 1235821, 1466519, 1598507, 1644497, 1789391, 1987849, 3401831, 3079553, 2706679, 3551921, 3571741, 5041723

Offset

2,1

Links

Robert Israel, Table of n, a(n) for n = 2..10000

Example

a(2) = 3*3+5*5+7*7 = 83 is prime.
a(3) = 3*3+5*5+7*7+11*11+13*13 = 373 is prime.
a(4) = 3*7+5*11+7*13+11*17+13*19+17*23+19*29 = 1543 is prime.

Maple

f:= proc(n) local B, C, i, k, t;
  B:= [seq(ithprime(i), i=2..2*n)];
  C:= [seq(ithprime(i), i=1..2*n-1)];
  for k from 1 do
    t:= add(B[i]*C[i], i=1..2*n-1);
    if isprime(t) then return t fi;
    C:= [op(C[2..-1]), nextprime(C[-1])];
  od
end proc:
map(f, [$2..100]);

Crossrefs

Sequence in context: A327850 A061525 A293979 * A160359 A142496 A142560

Adjacent sequences: A340858 A340859 A340860 * A340862 A340863 A340864

Keyword

nonn

Author

J. M. Bergot and Robert Israel, Jan 24 2021

Status

approved