A106476 - OEIS

A106476

Sequence array of Euler phi function.

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

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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;

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 A331447 A352460

Adjacent sequences: A106473 A106474 A106475 * A106477 A106478 A106479

KEYWORD

easy,nonn,tabl

AUTHOR

Paul Barry, May 03 2005

STATUS

approved