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A106476
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Sequence array of Euler phi function.
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1
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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; refs; listen; history; internal format)
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OFFSET
| 0,4
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COMMENTS
| 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
| Number triangle T(n, k)=if(k<=n, phi(n-k+1), 0)
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EXAMPLE
| 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
| Sequence in context: A090806 A174446 A071201 * A101566 A176653 A174842
Adjacent sequences: A106473 A106474 A106475 * A106477 A106478 A106479
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KEYWORD
| easy,nonn,tabl
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AUTHOR
| Paul Barry (pbarry(AT)wit.ie), May 03 2005
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