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Search: id:A130881
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| A130881 |
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Numbers n such that n = Sum_digits[(n+k)*abs(n-k)] for some k>=0. |
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1
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| 0, 1, 8, 9, 10, 17, 18, 26, 27, 35, 36, 44, 45, 53, 54, 62, 63, 71, 72, 80, 81, 89, 90, 98, 99, 107, 108, 116, 117, 125, 126, 134, 135, 143, 144, 152, 153, 161, 162, 170, 171, 179, 180, 188, 189, 197, 198, 206, 207, 215, 216, 224, 225, 233, 234, 242, 243, 251, 252
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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The first difference is eventually 2-periodic: 1, 7, 1, 1, 7, 1, 8, 1, 8, 1, 8, etc. The minimum numbers k associated to the first elements of the sequence are (n,k): (0,0), (1,0), (8,9), (9,0), (10,3), (17,24), (18,6), (26,75), etc.
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EXAMPLE
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n = 27 -> k = 75 -> (27+75)*abs(27-75)=102*48=4896 -> 4+8+9+6 = 27
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MAPLE
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P:=proc(n) local i, j, k, w; for i from 0 by 1 to n do for j from 0 by 1 to 100*n do w:=0; k:=(j+i)*abs(i-j); while k>0 do w:=w+k-(trunc(k/10)*10); k:=trunc(k/10); od; if w=i then print(i); break; fi; od; od; end: P(100000);
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CROSSREFS
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Sequence in context: A070480 A135043 A054966 this_sequence A048020 A048000 A048081
Adjacent sequences: A130878 A130879 A130880 this_sequence A130882 A130883 A130884
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KEYWORD
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nonn,base
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AUTHOR
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Paolo P. Lava & Giorgio Balzarotti (ppl(AT)spl.at), Jul 26 2007
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