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 A046657 a(n) = A002088(n)/2. 7
 1, 2, 3, 5, 6, 9, 11, 14, 16, 21, 23, 29, 32, 36, 40, 48, 51, 60, 64, 70, 75, 86, 90, 100, 106, 115, 121, 135, 139, 154, 162, 172, 180, 192, 198, 216, 225, 237, 245, 265, 271, 292, 302, 314, 325, 348, 356, 377, 387, 403, 415, 441, 450, 470, 482 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,2 COMMENTS a(n) = |{(x,y) : 1 <= x <= y <= n, x + y <= n, 1 = gcd(x,y)}| = |{(x,y) : 1 <= x <= y <= n, x + y > n, 1 = gcd(x,y)}|. - Steve Butler, Mar 31 2006 Brousseau proved that if the starting numbers of a generalized Fibonacci sequence are <= n (for n > 1) then the number of such sequences with relatively prime successive terms is a(n). - Amiram Eldar, Mar 31 2017 LINKS Giovanni Resta, Table of n, a(n) for n = 2..10000 Alfred Brousseau, A Note on the Number of Fibonacci Sequences, The Fibonacci Quarterly, Vol. 10, No. 6 (1972), pp. 657-658. FORMULA a(n) = 1/2 + Sum_{isum(numtheory[phi](k), k=1..n): seq(a(n)/2, n=2..60); # Muniru A Asiru, Mar 05 2018 MATHEMATICA Rest@ Accumulate[EulerPhi@ Range@ 56]/2 (* Michael De Vlieger, Apr 02 2017 *) PROG (PARI) a(n) = sum(k=1, n, eulerphi(k))/2; \\ Michel Marcus, Apr 01 2017 (GAP) List([2..60], n->Sum([1..n], k->Phi(k)/2)); # Muniru A Asiru, Mar 05 2018 CROSSREFS Cf. A002088. Partial sums of A023022. Sequence in context: A284685 A113238 A104214 * A102825 A070991 A225527 Adjacent sequences:  A046654 A046655 A046656 * A046658 A046659 A046660 KEYWORD nonn AUTHOR STATUS approved

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Last modified August 24 03:51 EDT 2019. Contains 326260 sequences. (Running on oeis4.)