cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-3 of 3 results.

A095901 A004001 (mod 2).

Original entry on oeis.org

1, 1, 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 1, 0, 1, 0, 0, 1, 0, 0, 1, 1, 1, 0, 1, 1, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 1, 1, 0, 1, 1, 0, 0, 0, 1, 0, 1, 1, 0, 1, 1, 0, 0, 0, 1, 0, 0, 1, 1, 1, 0, 0, 0
Offset: 1

Views

Author

Robert G. Wilson v, Jun 12 2004

Keywords

Crossrefs

Cf. A095902 (number of odd entries less than or equal to 2^n).
Cf. A283480 (partial sums).
Characteristic function of A283481.

Programs

  • Mathematica
    a[1] = a[2] = 1; a[n_] := a[n] = a[a[n - 1]] + a[n - a[n - 1]]; Table[ a[n], {n, 105}]
  • Scheme
    (define (A095901 n) (A000035 (A004001 n))) ;; Further code found under those two entries, Antti Karttunen, Mar 21 2017

Formula

a(n) = A004001(n) mod 2.

A283481 Positions of odd terms in A004001.

Original entry on oeis.org

1, 2, 5, 9, 11, 12, 17, 19, 22, 25, 26, 27, 33, 35, 37, 38, 40, 43, 46, 47, 48, 50, 51, 55, 56, 57, 58, 65, 67, 69, 72, 74, 77, 79, 80, 82, 83, 87, 89, 90, 92, 93, 97, 100, 101, 102, 107, 110, 111, 112, 117, 118, 119, 120, 121, 129, 131, 133, 135, 136, 138, 140, 143, 145, 148, 150, 151, 153, 154, 158, 160, 163, 165, 166, 168, 169
Offset: 1

Views

Author

Antti Karttunen, Mar 18 2017

Keywords

Crossrefs

Cf. A283482 (complement), A283480 (a left inverse).
Positions of ones in A095901.
Cf. A004001.

Programs

Formula

Other identities. For all n >= 1:
A283480(a(n)) = n.

A095902 Number of odd entries in A004001 that are <= 2^n.

Original entry on oeis.org

1, 2, 2, 3, 6, 12, 27, 55, 115, 235, 490, 994, 2008, 4036, 8120, 16280, 32640, 65344, 130879, 261935, 524057, 1048301, 2096855, 4193951, 8388239, 16776799, 33554339, 67109539, 134220995
Offset: 0

Views

Author

Robert G. Wilson v, Jun 12 2004

Keywords

Comments

Even entries and odd entries are equal only when n=4, 6 and 12. Past that, the evens outnumber the odds.

Crossrefs

Programs

  • Mathematica
    a[1] = a[2] = 1; a[n_] := a[n] = a[a[n - 1]] + a[n - a[n - 1]]; c = 0; k = 1; Do[ While[k <= 2^n, If[ Mod[ a[k], 2] == 1, c++ ]; k++ ]; Print[c], {n, 21}]
  • Scheme
    (define (A095902 n) (A283480 (A000079 n))) ;; Antti Karttunen, Mar 21 2017

Formula

a(n) = A283480(2^n) - Antti Karttunen, Mar 21 2017

Extensions

a(22)-a(28) from Donovan Johnson, Jan 28 2009
Showing 1-3 of 3 results.