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A026395
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T(n,0) + T(n,1) + ... + T(n,n), where T is array in A026386.
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0
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1, 2, 4, 10, 20, 50, 100, 250, 500, 1250, 2500, 6250, 12500, 31250, 62500, 156250, 312500, 781250, 1562500, 3906250, 7812500, 19531250, 39062500, 97656250, 195312500, 488281250, 976562500, 2441406250, 4882812500, 12207031250
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| a(n) is the number of irreducible representations of the Heisenberg group over the Gaussian integers into complex matrices of size 5^n x 5^n. [From Shannon Ezzat (sez10(AT)math.canterbury.ac.nz), Jan 20 2009]
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LINKS
| Index to sequences with linear recurrences with constant coefficients, signature (0,5)
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FORMULA
| G.f.: (1+2x-x^2)/(1-5x^2). - R. Stephan, Apr 30 2004
Contribution from Shannon Ezzat (sez10(AT)math.canterbury.ac.nz), Jan 20 2009: (Start)
a(n) = a(n-1) + 2*5^(n/2 -1) if n is even, a(n) = a(n-2) + 2*phi(5^[(n-1)/2]) if n is odd, where phi is the Euler phi function. (End)
For n > 3: a(n) = a(n-2)*a(n-1)/a(n). [Reinhard Zumkeller, Mar 06 2011]
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CROSSREFS
| Sequence in context: A094536 A003407 A151523 * A090246 A104442 A104434
Adjacent sequences: A026392 A026393 A026394 * A026396 A026397 A026398
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KEYWORD
| nonn
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AUTHOR
| Clark Kimberling (ck6(AT)evansville.edu)
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