

A141481


Square spiral of sums of selected preceding terms, starting at 1.


7



1, 1, 2, 4, 5, 10, 11, 23, 25, 26, 54, 57, 59, 122, 133, 142, 147, 304, 330, 351, 362, 747, 806, 880, 931, 957, 1968, 2105, 2275, 2391, 2450, 5022, 5336, 5733, 6155, 6444, 6591, 13486, 14267, 15252, 16295, 17008, 17370, 35487, 37402, 39835, 42452, 45220
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OFFSET

1,3


COMMENTS

Enter 1 into center position of the spiral. Repeat: Go to next position of the spiral and enter into that position the sum of the numbers in those already filled positions that are horizontally, vertically or diagonally adjacent to it.
Clockwise and counterclockwise construction of the spiral result in the same sequence.


LINKS

Klaus Brockhaus, Table of n, a(n) for n=1..961


EXAMPLE

Clockwise constructed spiral begins
362..747..806..880..931
351...11...23...25...26
330...10....1....1...54
304....5....4....2...57
147..142..133..122...59


PROG

(PARI) {m=5; h=2*m1; A=matrix(h, h); print1(A[m, m]=1, ", "); T=[[1, 0], [1, 1], [0, 1], [ 1, 1], [ 1, 0], [ 1, 1], [0, 1], [1, 1]]; for(n=1, (h2)^21, g=sqrtint(n); r=(g+g%2)\2; q=4*r^2; d=nq; if(n<=q2*r, j=d+3*r; k=r, if(n<=q, j=r; k=dr, if(n<=q+2*r, j=rd; k=r, j=r; k=d3*r))); j=j+m; k=k+m; s=0; for(c=1, 8, v=[j, k]; v+=T[c]; s=s+A[v[1], v[2]]); A[j, k]=s; print1(s, ", "))} [From Klaus Brockhaus, Aug 27 2008]


CROSSREFS

Cf. A063826, A094767, A094768, A094769, A126937.
Sequence in context: A091856 A083416 A022770 * A241268 A285697 A047611
Adjacent sequences: A141478 A141479 A141480 * A141482 A141483 A141484


KEYWORD

nonn


AUTHOR

Niclas Rantala (nrantala(AT)hotmail.com), Aug 09 2008


EXTENSIONS

Edited and extended beyond a(9) by Klaus Brockhaus, Aug 27 2008


STATUS

approved



