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A082209
a(1) = 1, a(n) = smallest number such that the concatenation of a(n-1) and a(n) is a square.
6
1, 6, 4, 9, 61, 504, 1, 6, 4, 9, 61, 504, 1, 6, 4, 9, 61, 504, 1, 6, 4, 9, 61, 504, 1, 6, 4, 9, 61, 504, 1, 6, 4, 9, 61, 504, 1, 6, 4, 9, 61, 504, 1, 6, 4, 9, 61, 504, 1, 6, 4, 9, 61, 504, 1, 6, 4, 9, 61, 504, 1, 6, 4, 9, 61, 504, 1, 6, 4, 9, 61, 504, 1, 6, 4, 9, 61, 504, 1, 6, 4, 9, 61
OFFSET
1,2
FORMULA
Periodic with period 6. - Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 20 2003
EXAMPLE
a(4) = 9 hence a(5) = 61 and 961 = 31^2.
MATHEMATICA
PadRight[{}, 120, {1, 6, 4, 9, 61, 504}] (* Harvey P. Dale, May 04 2013 *)
LinearRecurrence[{0, 0, 0, 0, 0, 1}, {1, 6, 4, 9, 61, 504}, 83] (* Ray Chandler, Aug 26 2015 *)
CoefficientList[ Series[ (504x^5 + 61x^4 + 9x^3 + 4x^2 + 6x + 1)/(1 - x^6), {x, 0, 83}], x] (* Robert G. Wilson v, Nov 22 2015 *)
PROG
(Magma) &cat [[1, 6, 4, 9, 61, 504]: n in [0..20]]; // Vincenzo Librandi, Nov 23 2015
(PARI) A082209(n)=[1, 6, 4, 9, 61, 504][(n-1)%6+1] \\ M. F. Hasler, Nov 24 2015
CROSSREFS
Cf. A082210.
See A090566 for another version.
Sequence in context: A334445 A168198 A177898 * A264770 A143520 A075450
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Apr 10 2003
EXTENSIONS
Corrected and extended by Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 20 2003
STATUS
approved