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 A046791 A046790 has several definitions, one of which is: "Numbers i such that there is a smaller positive number j such that (i+j)/2 and sqrt(i*j) are integers". The present sequence gives the smallest choice for j. 3
 2, 1, 4, 2, 6, 1, 3, 2, 4, 10, 5, 12, 1, 2, 6, 14, 7, 4, 2, 3, 20, 1, 22, 10, 6, 2, 11, 4, 26, 12, 28, 13, 30, 1, 5, 14, 2, 15, 34, 4, 3, 6, 38, 17, 10, 2, 42, 1, 19, 7, 44, 20, 46, 21, 12, 4, 22, 2, 23, 52, 6, 14, 1, 58, 26, 60, 2, 3, 5, 62, 10, 28, 4, 29, 66, 30, 68, 11, 31, 70, 2, 1, 6, 74, 33 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Note that A046790 is the complement of A078779. - Omar E. Pol, Jun 11 2016 LINKS David A. Corneth, Table of n, a(n) for n = 1..10000 FORMULA Let b(n)=A046790(n). Let k=k(n) be the greatest number whose square divides b(n) and is such that b(n) and b(n)/k^2 are of the same parity. Then a(n) = b(n)/k^2. - Vladimir Shevelev, Jun 07 2016 Or, equivalently, a(n) is the squarefree part s(n) of b(n), if either b(n) is odd or s(n) is even. Otherwise, when b(n) is even, but s(n) is odd, a(n)=4*s(n). - David A. Corneth, Jun 07 2016 EXAMPLE From Vladimir Shevelev, Jun 07 2016: (Start) A046790(5)=24 with even squarefree part (6), so a(5) = 6; A046790(12)=48 with odd squarefree part (3), so a(12) = 3*4=12. (End) PROG (PARI) a(n) = my(n=A046790(n), f=factor(n), p=n%2); f[, 2]=f[, 2]%2; r=prod(i=1, matsize(f), f[i, 1]^f[i, 2]); r*=(4^(n%2==0&&r%2==1)) \\ David A. Corneth, Jun 07 2016 CROSSREFS Cf. A046790. Sequence in context: A141564 A239641 A249151 * A187203 A187202 A125131 Adjacent sequences:  A046788 A046789 A046790 * A046792 A046793 A046794 KEYWORD nonn AUTHOR David W. Wilson, Dec 11 1999 EXTENSIONS Entry revised by N. J. A. Sloane, with help from Don Reble and several OEIS editors. Jun 07 2016 STATUS approved

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Last modified August 4 02:10 EDT 2020. Contains 336201 sequences. (Running on oeis4.)