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A055812
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a(n) and floor[a(n)/5] are both squares; i.e. squares which remain squares when written in base 5 and last digit is removed.
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20
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0, 1, 4, 9, 49, 81, 324, 2209, 15129, 25921, 103684, 710649, 4870849, 8346321, 33385284, 228826129, 1568397609, 2687489281, 10749957124, 73681302249, 505019158609, 865363202001, 3461452808004
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| Contribution by M. F. Hasler, Jan 15 2012: (Start)
For the first 3 terms, the above "base 5" interpretation is questionable, since they have only 1 digit in base 5. It is understood that dropping this digit yields 0.
For analogs in other bases see A055792 (base 2), A055793 (base 3), A055808 (base 4), A055851 (base 6), A204517 (base 7), A204515 (base 8), A204503 (base 9) and A023110 (base 10).
Squares of A204520. The square roots of floor[a(n)/5] are given in A204521. (End)
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EXAMPLE
| a(4) = 49 because 49 = 7^2 = 144 base 5 and 14 base 5 = 9 = 3^2
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PROG
| (PARI) b=5; for(n=1, 2e9, issquare(n^2\b) & print1(n^2, ", ")) \\ - M. F. Hasler, Jan 15 2012
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CROSSREFS
| Sequence in context: A115711 A029791 A053961 * A061867 A019544 A053059
Adjacent sequences: A055809 A055810 A055811 * A055813 A055814 A055815
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KEYWORD
| base,nonn
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AUTHOR
| Henry Bottomley (se16(AT)btinternet.com), Jul 14 2000
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EXTENSIONS
| More terms added and offset changed to 1 by M. F. Hasler, Jan 15 2012
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