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A343039 a(1) = 1, for n > 1, a(n) is the smallest positive integer for which a(n-1) + n + a(n) is a square. 1
1, 1, 5, 7, 4, 6, 3, 5, 2, 4, 1, 3, 9, 2, 8, 1, 7, 11, 6, 10, 5, 9, 4, 8, 3, 7, 2, 6, 1, 5, 13, 4, 12, 3, 11, 2, 10, 1, 9, 15, 8, 14, 7, 13, 6, 12, 5, 11, 4, 10, 3, 9, 2, 8, 1, 7, 17, 6, 16, 5, 15, 4, 14, 3, 13, 2, 12, 1, 11 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..69.

Todor Szimeonov, A completive sequence.

MATHEMATICA

d[n_] := Floor[Sqrt[n] + 1]^2 - n; a[1] = 1; a[n_] := a[n] = d[a[n - 1] + n]; Array[a, 100] (* Amiram Eldar, Apr 03 2021 *)

PROG

(Python)

from math import isqrt

def aupton(terms):

  alst = [1]

  for n in range(2, terms+1):

    alst.append((isqrt(alst[-1] + n)+1)**2 - alst[-1] - n)

  return alst

print(aupton(79)) # Michael S. Branicky, Apr 03 2021

CROSSREFS

Sequence in context: A300081 A293843 A240946 * A021178 A201506 A198985

Adjacent sequences:  A343036 A343037 A343038 * A343040 A343041 A343042

KEYWORD

nonn

AUTHOR

Todor Szimeonov, Apr 03 2021

STATUS

approved

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Last modified June 22 12:56 EDT 2021. Contains 345380 sequences. (Running on oeis4.)