A332267 a(1) = 1; a(2) = 2; for n > 2, if a(n-1) > a(n-2) then a(n) = a(n-1) - a(n-2), otherwise a(n) = number of occurrences of a(n-1).

1, 2, 1, 2, 1, 3, 2, 3, 1, 4, 3, 3, 4, 1, 5, 4, 3, 5, 2, 4, 2, 5, 3, 6, 3, 7, 4, 5, 1, 6, 5, 5, 6, 1, 7, 6, 4, 6, 2, 6, 4, 7, 3, 8, 5, 7, 2, 7, 5, 8, 3, 9, 6, 7, 1, 8, 7, 7, 8, 1, 9, 8, 5, 9, 4, 8, 4, 9, 5, 10, 5, 11, 6, 8, 2, 8, 6, 9, 3, 10, 7, 9, 2, 9, 7

Offset

1,2

Links

Table of n, a(n) for n=1..85.

Example

a(9) = a(8) - a(7) = 3-2 = 1. The number of occurrences of 1 up to that point is 4, so a(10) = 4.

Prog

(PARI) a=[1, 2]; for(n=2, 99, a=concat(a, if(a[n]>a[n-1], a[n]-a[n-1], sum(i=1, n, a[i]==a[n])))); a \\ M. F. Hasler, May 22 2020, brackets fixed by David A. Corneth, May 22 2020
(PARI) first(n) = {n = max(n, 2); res = vector(n); freqs = vector(2); res[1] = 1; res[2] = 2; freqs[1] = 1; freqs[2] = 1; for(i = 3, n, d = res[i-1] - res[i-2]; if(d > 0, res[i] = d; freqs[d]++ , fr = freqs[res[i-1]]; res[i] = fr; if(fr > #freqs, freqs = concat(freqs, vector(fr - #freqs)); ); freqs[fr]++ ) ); res } \\ David A. Corneth, May 22 2020

Crossrefs

Sequence in context: A353304 A376719 A305974 * A161148 A143773 A323524

Adjacent sequences: A332264 A332265 A332266 * A332268 A332269 A332270

Keyword

nonn,easy,look

Author

Ali Sada, May 04 2020

Status

approved