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A331435 a(n) is the least positive k such that A028916(n) - k^2 is a fourth power. 8
1, 2, 1, 6, 5, 4, 10, 11, 10, 14, 15, 1, 14, 5, 9, 20, 21, 24, 19, 4, 6, 26, 26, 12, 14, 29, 16, 31, 29, 22, 24, 31, 34, 1, 26, 5, 28, 35, 40, 19, 41, 39, 44, 38, 29, 45, 42, 4, 6, 35, 51, 16, 46, 20, 51, 54, 55, 56, 56, 30, 52, 54, 34, 36, 56, 58, 40, 9, 11 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Rémy Sigrist, Table of n, a(n) for n = 1..10000

Rémy Sigrist, PARI program for A331435

Wikipedia, Friedlander-Iwaniec theorem

EXAMPLE

The first terms, alongside A028916(n), are:

  n   a(n)  A028916(n)

  --  ----  ----------------

   1     1    2 =  1^2 + 1^4

   2     2    5 =  2^2 + 1^4

   3     1   17 =  1^2 + 2^4

   4     6   37 =  6^2 + 1^4

   5     5   41 =  5^2 + 2^4

   6     4   97 =  4^2 + 3^4

   7    10  101 = 10^2 + 1^4

   8    11  137 = 11^2 + 2^4

   9    10  181 = 10^2 + 3^4

  10    14  197 = 14^2 + 1^4

PROG

(PARI) See Links section.

CROSSREFS

See A002331, A331521, A331522, A331523, A331524, A331525, A331526 and A331527 for similar sequences.

Cf. A000583, A028916.

Sequence in context: A118980 A090665 A021826 * A159927 A176443 A105225

Adjacent sequences:  A331432 A331433 A331434 * A331436 A331437 A331438

KEYWORD

nonn

AUTHOR

Rémy Sigrist, Jan 18 2020

STATUS

approved

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Last modified July 27 11:04 EDT 2021. Contains 346304 sequences. (Running on oeis4.)