A083744 a(1) = 1; if a(n-1) + n is composite then a(n) = a(n-1) + n, else a(n) = a(n-1).

1, 1, 4, 8, 8, 14, 21, 21, 30, 40, 51, 63, 76, 90, 105, 121, 138, 156, 175, 195, 216, 238, 261, 285, 310, 336, 363, 391, 420, 450, 481, 513, 546, 580, 615, 651, 688, 726, 765, 805, 846, 888, 931, 975, 1020, 1066, 1113, 1161, 1210, 1260, 1311, 1363, 1416, 1470

Offset

1,3

Links

Michael De Vlieger, Table of n, a(n) for n = 1..10000

Maple

a := proc(n) option remember: if n=1 then RETURN(1) fi: if isprime(a(n-1)+n) then RETURN(a(n-1)) else RETURN(a(n-1)+n) fi: end: for n from 1 to 100 do printf(`%d, `, a(n)) od: # James A. Sellers, May 19 2003

Mathematica

a083744[n_] := Block[{i, t = Table[1, {n}]},
  For[i = 2, i < n,
   If[CompositeQ[t[[i - 1]] + i], t[[i]] = t[[i - 1]] + i,
t[[i]] = t[[i - 1]]], i++]; t]; a083744[54] (* Michael De Vlieger, Dec 24 2014 *)
nxt[{n_, a_}]:={n+1, If[CompositeQ[a+n+1], a+n+1, a]}; NestList[nxt, {1, 1}, 60][[All, 2]] (* Harvey P. Dale, Oct 09 2019 *)

Crossrefs

Cf. A083743.

Sequence in context: A316316 A333288 A159786 * A255992 A273572 A273779

Adjacent sequences: A083741 A083742 A083743 * A083745 A083746 A083747

Keyword

easy,nonn

Author

Amarnath Murthy, May 05 2003

Extensions

More terms from James A. Sellers, May 19 2003

Status

approved