A378916 a(n) is the smallest positive integer having n decompositions of twice its value into sums of two noncomposite numbers.

1, 2, 7, 12, 21, 24, 30, 70, 42, 45, 57, 60, 75, 84, 90, 117, 126, 156, 105, 135, 150, 189, 180, 165, 234, 288, 303, 195, 231, 240, 210, 285, 255, 396, 378, 438, 357, 444, 345, 360, 315, 330, 603, 390, 480, 435, 462, 450, 546, 609, 627, 420, 663, 540, 555, 615

Offset

1,2

Comments

a(n) is the index of first n in A001031.

Links

David Consiglio, Jr., Table of n, a(n) for n = 1..200

David Consiglio, Jr., Python

Example

For n = 3 we have that the first 3 in A001031 has index 7 and twice 7 is 14 and 14 has 3 decompositions into sums of two noncomposite numbers as follows: [1 + 13], [3 + 11], [7 + 7], so a(3) = 7.

Crossrefs

Cf. A001031, A008578, A378917.

Sequence in context: A023669 A137401 A309150 * A333354 A119713 A213041

Adjacent sequences: A378913 A378914 A378915 * A378917 A378918 A378919

Keyword

nonn

Author

Omar E. Pol, Dec 12 2024

Extensions

More terms from David Consiglio, Jr., Dec 18 2024

Status

approved