A265423 (-1)^n + 50*floor(3n/2) - 100*floor(n/4).

1, 49, 151, 199, 201, 249, 351, 399, 401, 449, 551, 599, 601, 649, 751, 799, 801, 849, 951, 999, 1001, 1049, 1151, 1199, 1201, 1249, 1351, 1399, 1401, 1449, 1551, 1599, 1601, 1649, 1751, 1799, 1801, 1849, 1951, 1999, 2001, 2049, 2151, 2199, 2201, 2249, 2351, 2399, 2401, 2449, 2551, 2599, 2601, 2649, 2751, 2799, 2801

Offset

0,2

Comments

Also: solutions to b^2 = 1 mod 400. Occurs in the context of a problem concerning integer-valued percentages, see link.

Links

Table of n, a(n) for n=0..56.

R. Israel, in reply to E. Angelini, Percentages, SeqFan list, Dec 7, 2015.

Index entries for linear recurrences with constant coefficients, signature (1,0,0,1,-1).

Formula

a(n)=2*A265424(n)+1.

G.f.: (1+48*x+102*x^2+48*x^3+x^4)/(1-x-x^4+x^5). - Robert Israel, Dec 08 2015

Maple

seq((-1)^n + 50*floor(3*n/2) - 100*floor(n/4), n=0..100); # Robert Israel, Dec 08 2015

Prog

(PARI) A265423(n)=(-1)^n+n*3\2*50-n\4*100
(PARI) is_A265423(n)=Mod(n, 400)^2==1

Crossrefs

Sequence in context: A044381 A044762 A159247 * A226146 A339730 A338011

Adjacent sequences: A265420 A265421 A265422 * A265424 A265425 A265426

Keyword

nonn,easy,changed

Author

M. F. Hasler, Dec 08 2015

Status

approved