OFFSET
0,3
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
FORMULA
a(n) = c*n*(n-1), where c ~ 0.48....
EXAMPLE
a(8) = 18 + 8 - gcd(8,18) = 18 +8 -2 = 24.
MAPLE
a[0]:=1: for n to 50 do a[n]:=a[n-1]+n-gcd(n, a[n-1]) end do: seq(a[n], n=0.. 50); # Emeric Deutsch, Feb 28 2008
MATHEMATICA
RecurrenceTable[{a[n] == a[n - 1] + n - GCD[n, a[n - 1]], a[0] == 1}, a, {n, 0, 25}] (* G. C. Greubel, Oct 08 2016 *)
nxt[{n_, a_}]:={n+1, a+n+1-GCD[n+1, a]}; NestList[nxt, {0, 1}, 50][[All, 2]] (* Harvey P. Dale, Jun 19 2018 *)
PROG
(PARI) first(n)=my(v=vector(n)); v[1]=1; for(k=2, n, v[k]=v[k-1]+k-gcd(k, v[k-1])); concat(1, v) \\ Charles R Greathouse IV, Oct 08 2016
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Ctibor O. Zizka, Feb 15 2008, Feb 21 2008
EXTENSIONS
Corrected and extended by Emeric Deutsch, Feb 28 2008
STATUS
approved