A211964 Right triangle from the snowflake (or E-toothpick) structure of A161330 (see Comments lines for definition).

0, 1, 2, 3, 5, 6, 8, 10, 12, 15, 17, 20, 24, 25, 27, 29, 32, 37, 40, 47, 51, 56, 63, 67, 73, 80, 82, 86, 90, 95, 103, 109, 120, 128, 136, 145, 151, 158, 166, 174, 182, 187, 193, 203, 210, 221, 232, 241, 250, 262, 271, 285, 294, 304, 318, 329, 343, 353, 362, 371

Offset

0,3

Comments

If n >> 1 the structure looks like a right triangle, which is essentially half of one of the six wedges of the E-toothpick (or snowflake) structure of A161330. The sequence gives the number of E-toothpicks in the structure after n stages. A211976 (the first differences) gives the number added at the n-th stage.

Links

Table of n, a(n) for n=0..59.

N. J. A. Sloane, A single E-toothpick

N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS

Index entries for sequences related to cellular automata

Index entries for sequences related to toothpick sequences

Formula

a(n) = (((A161330(n+1) - 2)/6) + n)/2.

a(n) = A220478(n)/2. - Omar E. Pol, Feb 19 2012

Crossrefs

Cf. A139250, A161328, A161330, A213360, A213366, A211976, A220478.

Sequence in context: A224955 A006856 A249013 * A140199 A072190 A363658

Adjacent sequences: A211961 A211962 A211963 * A211965 A211966 A211967

Keyword

nonn

Author

Omar E. Pol, Dec 17 2012

Status

approved