A363653 - OEIS

A363653

a(1) = 1; for n > 1, a(n) = a(n-1) - A000005(n) if a(n) strictly positive, else a(n) = a(n-1) + A000005(n).

1, 3, 1, 4, 2, 6, 4, 8, 5, 1, 3, 9, 7, 3, 7, 2, 4, 10, 8, 2, 6, 2, 4, 12, 9, 5, 1, 7, 5, 13, 11, 5, 1, 5, 1, 10, 8, 4, 8, 16, 14, 6, 4, 10, 4, 8, 6, 16, 13, 7, 3, 9, 7, 15, 11, 3, 7, 3, 1, 13, 11, 7, 1, 8, 4, 12, 10, 4, 8, 16, 14, 2, 4, 8, 2, 8, 4, 12, 10, 20, 15, 11, 9, 21

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OFFSET

1,2

COMMENTS

Variation on Recamán's sequence A005132.

LINKS

Table of n, a(n) for n=1..84.

EXAMPLE

a(1) = 1

a(2) = 1 + A000005(2) = 3

MATHEMATICA

a[1] = 1; a[n_] := a[n] = Module[{d = DivisorSigma[0, n]}, If[a[n - 1] > d, a[n - 1] - d, a[n - 1] + d]]; Array[a, 100] (* Amiram Eldar, Jun 13 2023 *)

CROSSREFS

Cf. A000005, A005132, A008343, A008344, A046901, A063733, A336760.

Sequence in context: A309636 A309650 A139432 * A202154 A115208 A234930

Adjacent sequences: A363650 A363651 A363652 * A363654 A363655 A363656

KEYWORD

nonn

AUTHOR

Ctibor O. Zizka, Jun 13 2023

STATUS

approved