A076466 a(1)=1 a(n) = a(n-1) + ((-1)^a(n-1)*a(n-1)) mod n.

1, 2, 4, 4, 8, 10, 13, 16, 23, 30, 38, 40, 41, 42, 54, 60, 69, 72, 87, 100, 116, 122, 129, 144, 163, 182, 202, 208, 213, 240, 263, 288, 312, 318, 321, 324, 352, 362, 373, 400, 431, 462, 494, 504, 513, 552, 587, 624, 660, 670, 677, 728, 767, 810, 850, 860, 865

Offset

1,2

Links

Table of n, a(n) for n=1..57.

Formula

a(n) is asymptotic to 4n^2/15; a(n)=4n^2/15 if n is of the form 30*(2k+1) hence a(60k+30) = 1800*(2k+1)^2

Example

a(8) = a(7) + ( (-1)^a(7)*a(7)) mod 8 = 13 + (- 13) mod 8 = 13 + 3 = 16

Mathematica

RecurrenceTable[{a[1]==1, a[n]==a[n-1]+Mod[(-1)^a[n-1] a[n-1], n]}, a, {n, 60}] (* Harvey P. Dale, Nov 09 2011 *)

Prog

(PARI) a(n)=a(n-1)+((-1)^a(n-1)*a(n-1))%n

Crossrefs

Sequence in context: A233394 A029599 A213064 * A073117 A342695 A039879

Adjacent sequences: A076463 A076464 A076465 * A076467 A076468 A076469

Keyword

nonn

Author

Benoit Cloitre, Nov 07 2002

Status

approved