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 A269903 Integers n such that A002110(n) / 2 is the sum of 4 but no fewer nonzero squares. 1
 3, 6, 7, 10, 14, 17, 20, 21, 26, 29, 30, 37, 40, 43, 44, 47, 50, 51, 58, 63, 67, 68, 72, 75, 82, 85, 90, 94, 97, 98, 102, 105, 106, 117, 120, 123, 125, 127, 129, 132, 139, 140, 143, 146, 150, 154, 164, 165, 167, 170, 173, 174, 178, 186, 190, 191, 193, 201, 205, 208, 209, 213, 220 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Chai Wah Wu, Table of n, a(n) for n = 1..10000 EXAMPLE 3 is a term because 3*5 = x^2 + y^2 + z^2 where x, y, z are integers is not soluble. 6 is a term because 3*5*7*11*13 = x^2 + y^2 + z^2 where x, y, z are integers is not soluble. 4 is not a term because 3*5*7 = x^2 + y^2 + z^2 where x, y, z are integers is soluble, 105 = 1^2 + 2^2 + 10^2. PROG (PARI) isA004215(n) = { my(fouri, j) ; fouri=1 ; while( n >=7*fouri, if( n % fouri ==0, j= n/fouri-7 ; if( j % 8==0, return(1) ) ; ); fouri *= 4 ; ) ; return(0) ; } for(n=2, 1e3, if(isA004215(prod(k=2, n, prime(k))), print1(n, ", "))); (Python) from sympy import prime A269903_list, p = [], 1 for i in range(2, 10**6): p = (p*prime(i)) % 8 if p == 7: A269903_list.append(i) # Chai Wah Wu, Mar 07 2016 CROSSREFS Cf. A002110, A004215. Sequence in context: A284625 A047281 A182909 * A191103 A100468 A190685 Adjacent sequences: A269900 A269901 A269902 * A269904 A269905 A269906 KEYWORD nonn AUTHOR Altug Alkan, Mar 07 2016 STATUS approved

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Last modified September 29 19:47 EDT 2023. Contains 365776 sequences. (Running on oeis4.)