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Search: id:A080341
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| A080341 |
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Sum of the n first terms that are congruent to 1, 4 or 5 mod 6 (A047259). |
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+0
1
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| 1, 5, 10, 17, 27, 38, 51, 67, 84, 103, 125, 148, 173, 201, 230, 261, 295, 330, 367, 407, 448, 491, 537, 584, 633, 685, 738, 793, 851, 910, 971, 1035, 1100, 1167, 1237, 1308, 1381, 1457, 1534, 1613, 1695, 1778, 1863, 1951, 2040, 2131, 2225, 2320, 2417
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Number of edges needed in a sector of a hexagon of size n paved by rhombi coming from triangular/hexagonal lattices.
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FORMULA
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n^2+(n+1)/3 with integer division, that is n mod 3 = 0 : n^2+n/3 n mod 3 = 1 : n^2+(n-1)/3 n mod 3 = 2 : n^2+(n+1)/3
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PROGRAM
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// java or beanShell script for(int i=1, s=m=0; i<40; i++) { m= i%6; if((m==1)||(m==4)||(m==5)) System.out.print((s+=i)+", "); } for(int i=1; i<20; i++) System.out.print((i*i+(i+1)/3)+" ");
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CROSSREFS
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Cf. A047259.
Adjacent sequences: A080338 A080339 A080340 this_sequence A080342 A080343 A080344
Sequence in context: A098749 A034676 A076598 this_sequence A086653 A020642 A067253
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KEYWORD
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easy,nonn
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AUTHOR
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Christian Mercat (Integer.Sequence(AT)entrelacs.net), Mar 20 2003
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