The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A274382 a(n) = gcd(n, n*(n+1)/2 - sigma(n)). 2
 1, 2, 1, 1, 1, 3, 1, 1, 1, 1, 1, 2, 1, 1, 3, 1, 1, 6, 1, 4, 1, 1, 1, 24, 1, 1, 1, 14, 1, 3, 1, 1, 3, 1, 1, 1, 1, 1, 1, 10, 1, 3, 1, 2, 3, 1, 1, 4, 1, 2, 3, 4, 1, 3, 1, 4, 1, 1, 1, 6, 1, 1, 1, 1, 1, 3, 1, 4, 3, 1, 1, 3, 1, 1, 1, 2, 1, 3, 1, 2, 1, 1, 1, 14, 1, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Paolo P. Lava, Table of n, a(n) for n = 1..10000 FORMULA a(n) = gcd(n, A000217(n)-A000203(n)). - Felix Fröhlich, Jun 23 2016 a(n) = gcd(n, antisigma(n)) = gcd(n, A024816(n)). - Omar E. Pol, Jun 29 2016 EXAMPLE a(6) = 3 because 6*7/2 - sigma(6) = 21 - 12 = 9 and gcd(6,9) = 3. MAPLE with(numtheory); P:=proc(q) local n; for n from 1 to q do print(gcd(n, n*(n+1)/2-sigma(n))); od; end: P(10^3); MATHEMATICA Table[GCD[n, n (n+1)/2 - DivisorSigma[1, n]], {n, 100}] (* Vincenzo Librandi, Jun 25 2016 *) PROG (PARI) a(n) = gcd(n, n*(n+1)/2-sigma(n)) \\ Felix Fröhlich, Jun 23 2016 (MAGMA) [GCD(n, n*(n+1) div 2-SumOfDivisors(n)): n in [1..100]]; // Vincenzo Librandi, Jun 25 2016 CROSSREFS Cf. A009194, A024816. Sequence in context: A175432 A204118 A095025 * A318997 A069897 A257242 Adjacent sequences:  A274379 A274380 A274381 * A274383 A274384 A274385 KEYWORD nonn,easy AUTHOR Paolo P. Lava, Jun 23 2016 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified May 26 13:49 EDT 2020. Contains 334626 sequences. (Running on oeis4.)