A330822 a(n) = digsum(2^a(n-1)) with a(0) = 0.

0, 1, 2, 4, 7, 11, 14, 22, 25, 29, 41, 50, 76, 106, 142, 214, 313, 380, 508, 691, 875, 1184, 1687, 2243, 3164, 4126, 5578, 7855, 10676, 13981, 18659, 25421, 34277, 46409, 63023, 85658, 116248, 157660, 213892, 290554, 393145, 532838, 723451, 981020, 1328449, 1799363

Offset

0,3

Links

Chai Wah Wu, Table of n, a(n) for n = 0..78

Example

Starting with a(0) = 0.
a(1) = digsum(2^0) = digsum(1) = 1.
a(2) = digsum(2^1) = digsum(2) = 2.
a(3) = digsum(2^2) = digsum(4) = 4.
a(4) = digsum(2^4) = digsum(16) = 7.
etc.

Mathematica

a[0] = 0; a[n_] := a[n] = Total @ IntegerDigits[2^a[n-1]]; Array[a, 45, 0] (* Amiram Eldar, Jan 03 2020 *)

Prog

(PARI) a(n)={my(x=0); for(i=0, n-1, x=sumdigits(2^x)); x};
lista(nn)={my(x=0, v=vector(nn+1)); v[1]=0; for(i=1, nn, x=sumdigits(2^x); v[i+1]=x); v};
(Magma) a:=[0, 1]; [n le 2 select a[n] else &+Intseq(2^Self(n-1)):n in [1..50]]; // Marius A. Burtea, Jan 03 2020

Crossrefs

Cf. A001370, A007953, A131577.

Sequence in context: A027427 A306070 A262136 * A018385 A361004 A372058

Adjacent sequences: A330819 A330820 A330821 * A330823 A330824 A330825

Keyword

nonn,base

Author

Haris Ziko, Jan 02 2020

Status

approved