A085111 a(1) = 1; then add 1, multiply by 2, subtract 3, multiply by 4, add 5, multiply by 6, subtract 7, multiply by 8 and so on.

1, 2, 4, 1, 4, 9, 54, 47, 376, 385, 3850, 3839, 46068, 46081, 645134, 645119, 10321904, 10321921, 185794578, 185794559, 3715891180, 3715891201, 81749606422, 81749606399, 1961990553576, 1961990553601, 51011754393626, 51011754393599, 1428329123020772

Offset

1,2

Links

Michael S. Branicky, Table of n, a(n) for n = 1..808

Prog

(Python)
from itertools import count, islice
def agen(): # generator of terms
    an = 1
    for n in count(1):
        yield an
        if n&1: an += (n if n&3 == 1 else -n)
        else: an *= n
print(list(islice(agen(), 30))) # Michael S. Branicky, Aug 09 2022

Crossrefs

Sequence in context: A256696 A244261 A361873 * A181332 A204021 A236471

Adjacent sequences: A085108 A085109 A085110 * A085112 A085113 A085114

Keyword

nonn

Author

Amarnath Murthy, Jul 04 2003

Extensions

More terms from Ray G. Opao, Apr 15 2004

a(26) and beyond from Michael S. Branicky, Aug 09 2022

Status

approved