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.

A211969 Triangle of decimal equivalents of binary numbers with some initial repeats, A211968.

Original entry on oeis.org

3, 6, 7, 10, 12, 13, 14, 15, 20, 21, 24, 25, 26, 27, 28, 29, 30, 31, 36, 40, 41, 42, 43, 45, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 72, 73, 80, 81, 82, 83, 84, 85, 86, 87, 90, 91, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106
Offset: 2

Views

Author

Omar E. Pol, Dec 03 2012

Keywords

Examples

			Irregular triangle begins, starting at row 2:
3;
6, 7;
10, 12, 13, 14, 15;
20, 21, 24, 25, 26, 27, 28, 29, 30, 31;
36, 40, 41, 42, 43, 45, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63;
		

Crossrefs

Complement of A211967.
Row lengths give: A093370.
Column 1 gives: A005418(n+1).
Right border gives: A000225(n).

Programs

  • Maple
    s:= proc(n) s(n):= `if`(n=1, [[1]], map(x->
          [[x[], 0], [x[], 1]][], s(n-1))) end:
    T:= proc(n) map (x-> add(x[i]*2^(nops(x)-i), i=1..nops(x)), select
          (proc(l) local i; for i to iquo(nops(l), 2) do if l[1..i]=
          l[i+1..2*i] then return true fi od; false end, s(n)))[] end:
    seq (T(n), n=2..7);  # Alois P. Heinz, Dec 04 2012