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A172090 Let f(0) = 1, f(1) = -2, f(n) = n*f(n-1) - 2 if |f(n-1)| is prime and f(n) = n*f(n-1)/(n+1) otherwise.  Then t(n,m) = f(n-m) + f(m) - f(n). 0
1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

Row sums are 1, 2, 4, 4, 4, 4, 4, 4, 4, 4, 4, ...; f(n) is 1, -2, -6, -9, -12, -15, -18, -21, -24, -27, -30, -33, -36, -39, -42, -45, -48, -51, -54, -57, -60, -63, -66, -69, -72, -75, -78, -81, -84, -87, -90, ....

LINKS

Table of n, a(n) for n=0..65.

EXAMPLE

{1},

{1, 1},

{1, 2, 1},

{1, 1, 1, 1},

{1, 1, 0, 1, 1},

{1, 1, 0, 0, 1, 1},

{1, 1, 0, 0, 0, 1, 1},

{1, 1, 0, 0, 0, 0, 1, 1},

{1, 1, 0, 0, 0, 0, 0, 1, 1},

{1, 1, 0, 0, 0, 0, 0, 0, 1, 1},

{1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1}

MATHEMATICA

f[0]=1; f[1]=-2;

f[n_]:=f[n]=If[PrimeQ[Abs[f[n-1]]], f[n-1]*n-2, f[n-1]*n/(n-1)];

Flatten[Table[Table[ -f[n]+f[n-k]+f[k], {k, 0, n}], {n, 0, 10}]]

CROSSREFS

Sequence in context: A316863 A037911 A176046 * A037912 A056980 A268643

Adjacent sequences:  A172087 A172088 A172089 * A172091 A172092 A172093

KEYWORD

nonn,tabl,uned

AUTHOR

Roger L. Bagula, Jan 25 2010

STATUS

approved

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Last modified June 6 18:59 EDT 2020. Contains 334832 sequences. (Running on oeis4.)