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A106476 Sequence array of Euler phi function. 1
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; text; internal format)
OFFSET

0,4

COMMENTS

Row sums are A002088(n+1). Diagonal sums are A106477. Riordan array (1/sum{j>=0, A106479(j)x^j},x).

LINKS

Table of n, a(n) for n=0..101.

FORMULA

Number triangle T(n, k)=if(k<=n, phi(n-k+1), 0)

EXAMPLE

Triangle begins

1;

1,1;

2,1,1;

2,2,1,1;

4,2,2,1,1;

2,4,2,2,1,1;

CROSSREFS

Sequence in context: A071201 A318045 A240656 * A101566 A176653 A174842

Adjacent sequences:  A106473 A106474 A106475 * A106477 A106478 A106479

KEYWORD

easy,nonn,tabl

AUTHOR

Paul Barry, May 03 2005

STATUS

approved

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Last modified February 21 11:25 EST 2019. Contains 320372 sequences. (Running on oeis4.)