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Pythagorean years: a Pythagorean year is one whose digits partition into two disjoint sets such that, considering digital sums, the Pythagorean relation 5^2=4^2 + 3^2 is evinced.
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%I #12 Apr 27 2012 16:36:34

%S 799,889,898,979,988,997,1699,1789,1798,1879,1888,1897,1969,1978,1987,

%T 1996,2599,2689,2698,2779,2788,2797,2869,2887,2896,2959,2968,2977,

%U 2986,2995,3499,3589,3598,3679,3688,3697,3769,3796,3859,3886,3895,3949,3958

%N Pythagorean years: a Pythagorean year is one whose digits partition into two disjoint sets such that, considering digital sums, the Pythagorean relation 5^2=4^2 + 3^2 is evinced.

%D J. P. Boudine, La geometrie de la chambre a air, pp. 88-90 Vuibert Paris 1998.

%e 1699 and 1888, for instance, are in the sequence (as are all permutations of them) because we have 1+6+9+9=(1+6+9)+9 and (1+8)+(8+8)=1+8+8+8.

%e All ordered solutions for years through 9999 follow with corresponding additional permutations:

%e 0799 -> {979,997,7099,7909,7990,9079,9097,9709,9790,9907,9970}

%e 0889 -> {898,988,8089,8098,8809,8890,8908,8980,9088,9808,9880}

%e 1699 -> {1969,1996,6199,6919,6991,9169,9196,9619,9691,9916,9961}

%e 1789 -> {1798,1879,1897,1978,1987,7189,7198,7819,7891,7918,7981,...}

%e 1888 -> {8188,8818,8881}

%e 2599 -> {2959,2995,5299,5929,5992,9259,9295,9529,9592,9925,9952}

%e 2689 -> {2698,2869,2896,2968,2986,6289,6298,6829,6892,6928,6982,...}

%e 2779 -> {2797,2977,7279,7297,7729,7792,7927,7972,9277,9727,9772}

%e 2788 -> {2878,2887,7288,7828,7882,8278,8287,8728,8782,8827,8872}

%e 3499 -> {3949,3994,4399,4939,4993,9349,9394,9439,9493,9934,9943}

%e 3589 -> {3598,3859,3895,3958,3985,5389,5398,5839,5893,5938,5983,...}

%e 3679 -> {3697,3769,3796,3967,3976,6379,6397,6739,6793,6937,6973,...}

%e 3688 -> {3868,3886,6388,6838,6883,8368,8386,8638,8683,8836,8863}

%e 4489 -> {4498,4849,4894,4948,4984,8449,8494,8944,9448,9484,9844}

%e 4579 -> {4597,4759,4795,4957,4975,5479,5497,5749,5794,5947,5974,...}

%e 4588 -> {4858,4885,5488,5848,5884,8458,8485,8548,8584,8845,8854}

%e 4669 -> {4696,4966,6469,6496,6649,6694,6946,6964,9466,9646,9664}

%e 5569 -> {5596,5659,5695,5956,5965,6559,6595,6955,9556,9565,9655}

%K nonn,base

%O 1,1

%A _Lekraj Beedassy_, Jan 21 2005

%E Extended by _Ray Chandler_, Jan 25 2005