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 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 (list; graph; refs; listen; history; text; internal format)
 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*m-1; 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, (h-2)^2-1, g=sqrtint(n); r=(g+g%2)\2; q=4*r^2; d=n-q; if(n<=q-2*r, j=d+3*r; k=r, if(n<=q, j=r; k=-d-r, if(n<=q+2*r, j=r-d; k=-r, j=-r; k=d-3*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

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