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A193139 Number of symmetric satins of order n. 2
0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 1, 0, 0, 3, 0, 0, 0, 1, 0, 1, 0, 1, 1, 0, 1, 1, 0, 0, 1, 3, 0, 1, 0, 1, 1, 0, 0, 3, 0, 0, 1, 1, 0, 0, 1, 3, 1, 0, 0, 3, 0, 0, 1, 1, 1, 1, 0, 1, 1, 1, 0, 3, 0, 0, 1, 1, 1, 1, 0, 3, 0, 0, 0, 3, 1, 0, 1, 3, 0, 1, 1, 1, 1, 0, 1, 3, 0, 0, 1, 1, 0, 1, 0, 3, 3, 0, 0, 1, 0, 1, 1, 3, 0, 1, 1, 1, 1, 0, 1, 7 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,22

LINKS

Table of n, a(n) for n=3..120.

B. Gr├╝nbaum and G. C. Shephard, Satins and twills: an introduction to the geometry of fabrics, Math. Mag., 53 (1980), 139-161. See Theorem 5.

FORMULA

a(n) = A157230(n) - 1. - Andrey Zabolotskiy, Dec 25 2018

MAPLE

V:=proc(n) local j, i, t1, t2, al, even;

t1:=ifactors(n)[2];

t2:=nops(t1);

if (n mod 2) = 0 then even:=1; al:=t1[1][2]; else even:=0; al:=0; fi;

j:=t2-even;

if (al <= 1) then RETURN(2^(j-1)-1); fi;

if (al = 2) then RETURN(2^j-1); fi;

if (al >= 3) then RETURN(2^(j+1)-1); fi;

end;

[seq(V(n), n=3..120)];

CROSSREFS

Cf. A193138, A193140, A157230.

Sequence in context: A085393 A128980 A096693 * A083206 A069531 A035677

Adjacent sequences:  A193136 A193137 A193138 * A193140 A193141 A193142

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Jul 16 2011

STATUS

approved

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Last modified October 20 10:45 EDT 2019. Contains 328257 sequences. (Running on oeis4.)