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 A267756 Indices of Euclid numbers (A006862) of the form x^2 + y^2 + z^2 where x, y and z are integers. 0
 0, 1, 4, 8, 11, 12, 13, 15, 16, 19, 22, 27, 31, 34, 35, 38, 41, 42, 46, 48, 52, 53, 56, 57, 61, 62, 64, 65, 66, 69, 70, 71, 73, 74, 76, 77, 78, 79, 80, 83, 84, 86, 87, 88, 89, 91, 93, 95, 99, 100, 103, 104, 107, 108, 111, 112, 113, 115, 116, 118, 119, 124, 128, 131, 133 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Corresponding Euclid numbers are 2, 3, 211, 9699691, 200560490131, 7420738134811, 304250263527211, 614889782588491411, 32589158477190044731, ... Complement of this sequence is 2, 3, 5, 6, 7, 9, 10, 14, 17, 18, 20, 21, 23, 24, 25, 26, 28, 29, 30, 32, 33, 36, 37, 39, 40, 43, 44, 45, 47, 49, 50, 51, 54, 55, 58, 59, 60, 63, 67, 68, 72, 75, 81, 82, 85, 90, 92, 94, 96, 97, 98, 101, ... Euclid numbers that are not of the form x^2 + y^2 + z^2 are 7, 31, 2311, 30031, 510511, 223092871, 6469693231, 13082761331670031, 1922760350154212639071, ... LINKS EXAMPLE 0 is a term because A006862(0) = 2 = 0^2 + 1^2 + 1^2. 1 is a term because A006862(1) = 3 = 1^2 + 1^2 + 1^2. 4 is a term because A006862(4) = 211 = 3^2 + 9^2 + 11^2. 8 is a term because A006862(8) = 9699691 = 79^2 + 123^2 + 3111^2. PROG (PARI) isA004215(n) = { local(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) ; } a006862(n) = prod(k=1, n, prime(k))+1; for(n=0, 200, if(!isA004215(a006862(n)), print1(n, ", "))); CROSSREFS Cf. A004215, A006862. Sequence in context: A311013 A311014 A311015 * A311016 A311017 A311018 Adjacent sequences:  A267753 A267754 A267755 * A267757 A267758 A267759 KEYWORD nonn AUTHOR Altug Alkan, Jan 20 2016 STATUS approved

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Last modified May 19 05:04 EDT 2022. Contains 353826 sequences. (Running on oeis4.)