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A038759 a(n) = ceiling(sqrt(n))*floor(sqrt(n)). 3
0, 1, 2, 2, 4, 6, 6, 6, 6, 9, 12, 12, 12, 12, 12, 12, 16, 20, 20, 20, 20, 20, 20, 20, 20, 25, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 36, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 49, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 64, 72, 72, 72, 72, 72, 72, 72 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

a(n)=n iff n is a square or a pronic (or heteromecic) number of form k(k+1). The sequence interleaves individual squares with 2k copies of each pronic.

LINKS

Table of n, a(n) for n=0..71.

FORMULA

a(n) = A003059(n)*A000196(n) = n - A038760(n).

EXAMPLE

a(31)=30 since 6 and 5 are on either side of the square root of 31 and 6*5=30.

CROSSREFS

Cf. A002378, A053187.

Sequence in context: A118960 A107797 A316788 * A045999 A075569 A062722

Adjacent sequences:  A038756 A038757 A038758 * A038760 A038761 A038762

KEYWORD

nonn

AUTHOR

Henry Bottomley, May 03 2000

STATUS

approved

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Last modified August 25 03:01 EDT 2019. Contains 326318 sequences. (Running on oeis4.)