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 A128251 n^4 - 1 divided by its largest fourth power divisor. 0
 15, 5, 255, 39, 1295, 150, 4095, 410, 9999, 915, 20735, 1785, 38415, 3164, 65535, 5220, 104975, 8145, 159999, 12155, 234255, 17490, 331775, 24414, 456975, 33215, 614655, 44205, 809999, 57720, 1048575, 74120, 1336335, 93789, 1679615, 117135 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 COMMENTS In other words, biquadratefree part of n^4-1, or biquadratefree kernel of n^4-1. Fourth power analog of what A128972 is to cubes and A068310 is to squares. A046100 Biquadratefree numbers. A008835 Largest 4th power dividing n. LINKS Eric Weisstein's World of Mathematics, Biquadratefree. FORMULA a(n) = (n^4 - 1)/A008835(n^4 - 1) = (A000583(n)-1)/A008835((A000583(n)-1)). EXAMPLE a(3) = 5 because (3^4 - 1)/16 = 80/16 = (2^4 * 5)/(2^4) = 5. a(5) = 39 because (5^4 - 1)/16 = 624/16 = (2^4 * 3 * 13)/(2^4) = 39. a(7) = 150 because (7^4 - 1)/16 = 2400/16 = (2^5 * 3 * 5^2)/(2^4) = 150. a(9) = 410 because (9^4 - 1)/16 = 6560/16 = (2^5 * 5 * 41)/(2^4) = 410. a(63) = 61535 because (63^4 - 1)/256 = 15752960/256 = (2^8 * 5 * 31 * 397)/(2^8) = 61535. CROSSREFS Cf. A000188, A000583, A002350, A004709, A007948, A008835, A062378, A067872, A033314, A068310, A128972. Sequence in context: A110791 A241361 A249996 * A292307 A064107 A116907 Adjacent sequences:  A128248 A128249 A128250 * A128252 A128253 A128254 KEYWORD easy,nonn AUTHOR Jonathan Vos Post, May 03 2007 STATUS approved

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Last modified July 18 01:14 EDT 2019. Contains 325110 sequences. (Running on oeis4.)