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A298990 Least number m such that A035026(m) = n. 1
1, 2, 4, 5, 8, 11, 12, 17, 18, 37, 24, 53, 30, 89, 39, 71, 42, 101, 45, 179, 57, 137, 72, 193, 60, 233, 84, 257, 90, 251, 117, 401, 123, 311, 144, 373, 120, 347, 105, 457, 162, 661, 150, 479, 180, 547, 237, 599, 165, 617, 264, 641, 288, 683, 195, 907, 231, 881 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

The upper branch visible in the scatterplot of the first terms corresponds to odd-indexed terms. - Rémy Sigrist, Jan 31 2018

LINKS

Rémy Sigrist, Table of n, a(n) for n = 0..10000

Rémy Sigrist, C++ program for A298990

EXAMPLE

2* 2 = 2 +  2,                                      so a(1) =  2.

2* 4 = 3 +  5 = 5 +  3,                             so a(2) =  4.

2* 5 = 3 +  7 = 5 +  5 =  7 +  3,                   so a(3) =  5.

2* 8 = 3 + 13 = 5 + 11 = 11 +  5 = 13 + 3,          so a(4) =  8.

2*11 = 3 + 19 = 5 + 17 = 11 + 11 = 17 + 5 = 19 + 3, so a(5) = 11.

PROG

(C++) See Links section.

(PARI) nb(n) = sum(i=1, 2*n-1, isprime(i) && isprime(2*n-i));

a(n) = {my(k=1); while (nb(k) != n, k++); k; } \\ Michel Marcus, Jan 31 2018

CROSSREFS

Cf. A035026.

Sequence in context: A174803 A282434 A105659 * A191169 A191122 A191338

Adjacent sequences:  A298987 A298988 A298989 * A298991 A298992 A298993

KEYWORD

nonn,changed

AUTHOR

Seiichi Manyama, Jan 31 2018

STATUS

approved

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Last modified December 16 09:06 EST 2019. Contains 330020 sequences. (Running on oeis4.)