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A121870
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Monthly Problem 10791, second expression.
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1
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1, 1, 2, 9, 61, 554, 6565, 96677, 1716730, 36072181, 881242577, 24674241834, 783024550969, 27896201305769, 1106485798248706, 48517267642373105, 2337333266369553253, 123040664089658462650, 7043260281573138384701, 436533086101058798529933
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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REFERENCES
| A. Fekete and others, Problem 10791, Amer. Math. Monthly, 108 (No. 2, 2001), 177-178.
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FORMULA
| Equals A121867(n)^2 + A121868(n)^2.
From Gary W. Adamson, Jul 22 2011: (start) Sqrt(a(n)) = upper left term in M^n as to the modulus of a polar term; M = an infinite square production matrix in which a column of (i, i, i,...) is appended to the right of Pascal's triangle, as follows (with i = sqrt(-1)):
1, i, 0, 0, 0,...
1, 1, i, 0, 0,...
1, 2, 1, i, 0,...
1, 3, 3, 1, i,...
... (end)
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EXAMPLE
| a(4) = 61 = square of upper left term of M^4, = the square of (sqrt(61)Angle 140.194....), where the modulus is squared, getting 61.
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MAPLE
| #To generate a(n), enter a number for n. A121870a:= proc(a) local i, t: i:=1: t:=0: for i to 100 do t:=t+evalf((i^(a-1))*(I)^i/(i)!): od:RETURN(round(abs(t^2))): end: a:= A121870a(n); - Russell Walsmith (ixitol(AT)gmail.com), Apr 18 2008
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CROSSREFS
| Cf. A121869, A024429, A024430, A121867, A121868.
Sequence in context: A107883 A088182 A006155 * A146887 A173498 A113662
Adjacent sequences: A121867 A121868 A121869 * A121871 A121872 A121873
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Sep 05 2006
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