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A061322 a(n) = a(n-1)*(1+a(n-1)/n^2) with a(0)=2. 1
2, 6, 15, 40, 140, 924, 24640, 12415040, 2408343949440, 71606426901226335015040, 51274803735606705472274088614112357905277056, 21728144612603201307908899563300049012978385050783094682272184269369267136230071558272 (list; graph; refs; listen; history; internal format)
OFFSET

0,1

COMMENTS

Only first 42 terms are integers (see A003504).

FORMULA

a(n+1) =a(n)+A003504(n+1)^2, a(n) =(n+1)*A003504(n+1) =A061314(2, n).

EXAMPLE

a(2)=6*(1+6/2^2)=15.

PROG

(PARI) a(n)=local(x); if(n<1, 2*(n==0), (x=a(n-1))+(x/n)^2) /* Michael Somos Apr 02 2006 */

CROSSREFS

Sequence in context: A001654 A062106 A206000 * A004664 A074446 A180666

Adjacent sequences:  A061319 A061320 A061321 * A061323 A061324 A061325

KEYWORD

nonn

AUTHOR

Henry Bottomley (se16(AT)btinternet.com), Apr 24 2001

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Last modified February 16 11:20 EST 2012. Contains 205907 sequences.