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Search: id:A073577
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| 7, 23, 47, 79, 119, 167, 223, 287, 359, 439, 527, 623, 727, 839, 959, 1087, 1223, 1367, 1519, 1679, 1847, 2023, 2207, 2399, 2599, 2807, 3023, 3247, 3479, 3719, 3967, 4223, 4487, 4759, 5039, 5327, 5623, 5927, 6239, 6559, 6887, 7223, 7567, 7919, 8279, 8647
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OFFSET
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1,1
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COMMENT
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Sums of squares of two consecutive elements multiplied (or divided) by 2 is always a perfect square. In general numbers represented by the quadratic form a(n)=(2*i*n+j)^2-2*i^2 for any i and j have 2(a(n)^2 + a(n+1)^2)) and (a(n)^2 + a(n+1)^2)/2 as perfect squares: in this case i=j=1.
The elements of this sequence may be seen to be 2 less than the odd squares. As such they run parallel to those in the square spiral as well as the Ulam square spiral. - Stuart M. Ellerstein (ellerstein(AT)aol.com), Oct 01 2002
a(n)=FrobeniusNumber[2n+1,2n+3] - Darrell Minor (dminor(AT)cscc.edu), Jul 29 2008
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CROSSREFS
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Sequence in context: A097149 A139035 A002146 this_sequence A139830 A101789 A062725
Adjacent sequences: A073574 A073575 A073576 this_sequence A073578 A073579 A073580
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KEYWORD
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nonn
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AUTHOR
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M. N. Deshpande (dpratap(AT)nagpur.dot.net.in), Aug 27 2002
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EXTENSIONS
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Edited and extended by Henry Bottomley (se16(AT)btinternet.com), = Oct 10 2002
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