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Search: id:A106476
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| A106476 |
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Sequence array of Euler phi function. |
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+0
2
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| 1, 1, 1, 2, 1, 1, 2, 2, 1, 1, 4, 2, 2, 1, 1, 2, 4, 2, 2, 1, 1, 6, 2, 4, 2, 2, 1, 1, 4, 6, 2, 4, 2, 2, 1, 1, 6, 4, 6, 2, 4, 2, 2, 1, 1, 4, 6, 4, 6, 2, 4, 2, 2, 1, 1, 10, 4, 6, 4, 6, 2, 4, 2, 2, 1, 1, 4, 10, 4, 6, 4, 6, 2, 4, 2, 2, 1, 1, 12, 4, 10, 4, 6, 4, 6, 2, 4, 2, 2, 1, 1, 6, 12, 4, 10, 4, 6, 4, 6, 2, 4, 2
(list; table; graph; listen)
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OFFSET
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0,4
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COMMENT
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Row sums are A002088(n+1). Diagonal sums are A106477. Riordan array (1/sum{j>=0, A106479(j)x^j},x).
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FORMULA
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Number triangle T(n, k)=if(k<=n, phi(n-k+1), 0)
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EXAMPLE
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Triangle begins
1;
1,1;
2,1,1;
2,2,1,1;
4,2,2,1,1;
2,4,2,2,1,1;
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CROSSREFS
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Sequence in context: A048570 A090806 A071201 this_sequence A101566 A156074 A051287
Adjacent sequences: A106473 A106474 A106475 this_sequence A106477 A106478 A106479
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KEYWORD
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easy,nonn,tabl
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), May 03 2005
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