OFFSET
1,1
LINKS
T. D. Noe, Table of n, a(n) for n = 1..10000
Patrick De Geest, WONplate 122
Carlos Rivera, Puzzle 46. Primes expressible as sum of consecutive primes in K ways, The Prime Puzzles and Problems Connection.
Eric Weisstein's World of Mathematics, Prime Sums
EXAMPLE
E.g., 5 = (2 + 3) or (#2,2).
2+3 = 5, 3+5 = 8, 2+3+5 = 10, 7+5 = 12, 3+5+7 = 15, etc.
MAPLE
# uses code of A084143
isA050936 := proc(n::integer)
if A084143(n) >= 1 then
true;
else
false;
end if;
end proc:
for n from 1 to 300 do
if isA050936(n) then
printf("%d, ", n);
end if;
end do: # R. J. Mathar, Aug 19 2020
MATHEMATICA
lst={}; Do[p=Prime[n]; Do[p=p+Prime[k]; AppendTo[lst, p], {k, n+1, 2*10^2}], {n, 2*10^2}]; Take[Union[lst], 10^2] (* Vladimir Joseph Stephan Orlovsky, Aug 21 2008 *)
f[n_] := Block[{len = PrimePi@ n}, p = Prime@ Range@ len; Count[ Flatten[ Table[ p[[i ;; j]], {i, len}, {j, i+1, len}], 1], q_ /; Total@ q == n]]; Select[ Range@ 150, f@ # > 0 &] (* Or quicker for a larger range *)
lmt = 150; p = Prime@ Range@ PrimePi@ lmt; t = Table[0, {lmt}]; Do[s = 0; j = i+1; While[s = s + p[[j]]; s <= lmt, t[[s]]++; j++], {i, Length@ p}]; Select[ Range@ lmt, t[[#]] > 0 &] (* Robert G. Wilson v *)
Module[{nn=70, prs}, prs=Prime[Range[nn]]; Take[Union[Flatten[Table[Total/@ Partition[prs, i, 1], {i, 2, nn}]]], nn]] (* Harvey P. Dale, Nov 13 2013 *)
PROG
(Haskell)
import Data.Set (empty, findMin, deleteMin, insert)
import qualified Data.Set as Set (null)
a050936 n = a050936_list !! (n-1)
a050936_list = f empty [2] 2 $ tail a000040_list where
f s bs c (p:ps)
| Set.null s || head bs <= m = f (foldl (flip insert) s bs') bs' p ps
| otherwise = m : f (deleteMin s) bs c (p:ps)
where m = findMin s
bs' = map (+ p) (c : bs)
-- Reinhard Zumkeller, Aug 26 2011
(PARI) is(n)=my(v, m=1, t); while(1, v=vector(m++); v[m\2]=precprime(n\m); for(i=m\2+1, m, v[i]=nextprime(v[i-1]+1)); forstep(i=m\2-1, 1, -1, v[i]=precprime(v[i+1]-1)); if(v[1]==0, return(0)); t=vecsum(v); if(t==n, return(1)); if(t>n, while(t>n, t-=v[m]; v=concat(precprime(v[1]-1), v[1..m-1]); t+=v[1]), while(t<n, t-=v[1]; v=concat(v[2..m], nextprime(v[m]+1)); t+=v[m])); if(v[1]==0, return(0)); if(t==n, return(1))) \\ Charles R Greathouse IV, May 05 2016
(PARI) list(lim)=my(v=List(), s, n=1, p); while(1, p=2; s=vecsum(primes(n++)); if(s>lim, return(Set(v))); listput(v, s); forprime(q=prime(n+1), , s+=q-p; if(s>lim, break); listput(v, s); p=nextprime(p+1))); \\ Charles R Greathouse IV, Nov 24 2021
CROSSREFS
KEYWORD
nice,nonn,easy
AUTHOR
G. L. Honaker, Jr., Dec 31 1999
EXTENSIONS
More terms from David W. Wilson, Jan 13 2000
STATUS
approved