A137411 Weak Goodstein sequence starting at 11.

11, 30, 67, 127, 217, 343, 511, 636, 775, 928, 1095, 1276, 1471, 1680, 1903, 2139, 2389, 2653, 2931, 3223, 3529, 3849, 4183, 4531, 4893, 5269, 5659, 6063, 6481, 6913, 7359, 7818, 8291, 8778, 9279, 9794, 10323, 10866, 11423, 11994, 12579, 13178

Offset

2,1

Comments

The sequence eventually goes to zero, as can be seen by noting that multiples of the highest exponent (3 in this case) only go down; in fact the 8th term, a(8) = 7*8^2 + 7*8 + 7 = 511; after which the multiple of the square term will only go down, etc.

This sequence, for 11, grows beyond the quintillions of digits before going to zero.

References

K. Hrbacek & T. Jech, Introduction to Set Theory, Taylor & Francis Group, 1999, pp. 125-127.

Links

Harvey P. Dale, Table of n, a(n) for n = 2..1000

Formula

To obtain a(n + 1), write a(n) in base n, increase the base to n + 1 and subtract 1.

Example

a(2) = 11 = 2^3 + 2^1 + 2^0
a(3) = 3^3 + 3^1 + 3^0 - 1 = 30
a(4) = 4^3 + 4^1 - 1 = 4^3 + 3*4^0 = 67

Mathematica

nxt[{n_, a_}]:={n+1, FromDigits[IntegerDigits[a, n+1], n+2]-1}; Transpose[ NestList[ nxt, {1, 11}, 50]][[2]] (* Harvey P. Dale, Feb 09 2015 *)

Crossrefs

Cf. A056004 (strong Goodstein sequences), A059933 (strong Goodstein sequence for 16.).

Sequence in context: A051682 A109943 A303856 * A002755 A346852 A157827

Adjacent sequences: A137408 A137409 A137410 * A137412 A137413 A137414

Keyword

nonn

Author

Nicholas Matteo (kundor(AT)kundor.org), Apr 15 2008

Status

approved