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

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A285308 Decimal expansion of the sum of the alternating series of reciprocals of cubed composite numbers. 0
 0, 1, 2, 2, 1, 0, 3, 4, 4, 6, 8, 7, 8, 2, 2, 3 (list; constant; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Using an approach similar to the one described in the Nov 10 2016 comments at A275712 (see the charts in that sequence's Links), I am confident that this constant is 0.01221034468782231413473583117487004398688..., with the next digit probably a 9. - Jon E. Schoenfield, Jan 16 2018 LINKS FORMULA Equals Sum_{k>=1} (-1)^(k+1)/(A002808(k)^3). EXAMPLE Equals 1/(4^3) - 1/(6^3) + 1/(8^3) - 1/(9^3) + ... = 0.0122103446878223... PROG (PARI) composite(n) = { local(c, x); c=1; x=1; while(c <= n, x++; if(!isprime(x), c++); ); return(x) } \p 35000 sumalt(k=1, (-1)^(k+1)/composite(k)^3) (PARI) upto(n) = my(c=4, s=1, t=0.); while(c<=n, t+=s/c^3; c++; while(isprime(c), c++); s=-s); t upto(n) = my(prev=3, s=1, t=0.); forprime(p=5, n, for(i=prev+1, p-1, t+=s/i^3; s=-s; prev=p)); s=-s; t+sum(i=prev+1, n, s=-s; s/i^3) \\ David A. Corneth, Apr 29 2017 CROSSREFS Cf. A002808, A269229, A275712, A276494. Sequence in context: A285099 A306754 A063250 * A276543 A107424 A155161 Adjacent sequences:  A285305 A285306 A285307 * A285309 A285310 A285311 KEYWORD nonn,cons,more AUTHOR Terry D. Grant, Apr 16 2017 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 January 18 15:35 EST 2021. Contains 340254 sequences. (Running on oeis4.)