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A008319
Smallest number that is sum of squares of distinct earlier terms.
0
1, 1, 2, 4, 5, 6, 16, 17, 18, 20, 21, 22, 25, 26, 27, 29, 30, 31, 36, 37, 38, 40, 41, 42, 43, 45, 46, 47, 52, 53, 54, 56, 57, 58, 61, 62, 63, 65, 66, 67, 77, 78, 79, 81, 82, 83, 256, 257, 258, 260, 261, 262, 272, 273, 274, 276, 277, 278, 281, 282, 283, 285, 286, 287, 289, 290, 291
OFFSET
1,3
COMMENTS
Up to a(99999680)=10^8, the largest number not in the sequence is 892. I also computed, up to a(99934078)=10^8, the similar sequence which starts with 1,2 instead of 1,1. The largest number not in that sequence seems to be 134179 - Giovanni Resta, Oct 06 2011
Resta's conjecture is correct. Let x = floor(sqrt(n) - 12). For n > 1935, x^2 > n/2. For n > 1853, n - x^2 > 892. So n > 1935 can be decomposed into x^2 plus a number greater than 892. Since the other number is smaller than x^2, any decomposition into squares will use only numbers smaller than x. By induction, all numbers greater than 1935 (and hence greater than 892) are in this sequence. - Charles R Greathouse IV, Oct 06 2011
REFERENCES
Mihaly Bencze [Beneze], Smarandache Recurrence Type Sequences, Bull. Pure Appl. Sciences, Vol. 16E, No. 2 (1997), pp. 231-236.
FORMULA
For n > 572, a(n) = n + 320. - Charles R Greathouse IV, Oct 06 2011
CROSSREFS
Sequence in context: A026473 A272929 A336129 * A033311 A098504 A137653
KEYWORD
nonn,easy,nice
AUTHOR
R. Muller
EXTENSIONS
More terms from David W. Wilson
STATUS
approved