A344794 - OEIS

A344794

a(n) is the least k such that A344793(k) = n.

1, 2, 10, 4, 8, 16, 12, 19, 25, 34, 36, 37, 53, 50, 48, 61, 73, 63, 114, 78, 93, 90, 88, 100, 119, 95, 110, 137, 130, 133, 155, 145, 159, 163, 172, 187, 189, 181, 180, 195, 227, 211, 224, 233, 243, 258, 237, 245, 266, 276, 273, 285, 303, 298, 345, 312, 310, 322, 321, 375, 351, 340, 352, 335, 372

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OFFSET

0,2

COMMENTS

a(n) is the least k such that there are exactly n primes of the form 2*prime(i)+prime(k) for i < k.

LINKS

Robert Israel, Table of n, a(n) for n = 0..690

EXAMPLE

a(6) = 12 because A344793(12) = 6 and this is the first appearance of the value 6 in A344793.

MAPLE

f:= proc(n) local i, p;

p:= ithprime(n);

numboccur(true, map(isprime, [seq(2*ithprime(i)+p, i=1..n-1)]))

end proc:

A:= map(f, [$1..2000]):

V:= Array(0..200):

for i from 1 to 2000 do

if A[i]<=200 and V[A[i]] = 0 then V[A[i]]:= i fi

od:

convert(V, list);

MATHEMATICA

A344793[n_] := A344793[n] = Module[{p, q},

p = Prime[n];

q = Select[Range[p - 1], PrimeQ];

Count[p + 2 q, _?PrimeQ]];

a[n_] := For[k = 1, True, k++, If[A344793[k] == n, Return[k]]];

Table[a[n], {n, 0, 100}] (* Jean-François Alcover, May 16 2023 *)

CROSSREFS

Cf. A344793.

Sequence in context: A344544 A364262 A102512 * A196364 A029673 A189881

Adjacent sequences: A344791 A344792 A344793 * A344795 A344796 A344797

KEYWORD

nonn

AUTHOR

J. M. Bergot and Robert Israel, May 28 2021

STATUS

approved