A061512 a(0) = 1; a(n) is obtained by incrementing each digit of a(n-1) by 2.

1, 3, 5, 7, 9, 11, 33, 55, 77, 99, 1111, 3333, 5555, 7777, 9999, 11111111, 33333333, 55555555, 77777777, 99999999, 1111111111111111, 3333333333333333, 5555555555555555, 7777777777777777, 9999999999999999, 11111111111111111111111111111111, 33333333333333333333333333333333

Offset

0,2

Comments

In A061511-A061522, A061746-A061750 when the incremented digit exceeds 9 it is written as a 2-digit string. So 9+1 becomes the 2-digit string 10, etc.

Also: odd repdigits (A010785) of length 2^k, cf. formula. - M. F. Hasler, Jun 24 2016

Links

Table of n, a(n) for n=0..26.

Formula

a(n) = (10^2^floor(n/5)-1)/9*(n%5*2+1), where n%5 means the remainder (in {0..4}) of n divided by 5. - M. F. Hasler, Jun 24 2016

Example

Following 33: 3+2 = 5 and 3+2 = 5, hence the next term is 55.

Mathematica

NestList[FromDigits[Flatten[IntegerDigits/@(IntegerDigits[#]+2)]]&, 1, 30] (* Harvey P. Dale, Apr 13 2012 *)

Prog

(PARI) A061512(n)=10^2^(n\5)\9*(n%5*2+1) \\ M. F. Hasler, Jun 24 2016
(PARI) nxt(n) = my(d=digits(n)); if(d[1]<9, n+2*(10^#d - 1)/9, (10^(2*#d) - 1)/9)
inv(n) = {my(d=digits(n)); 5*logint(#d, 2) + (d[1]+1)\2} \\ David A. Corneth, Jun 24 2016

Crossrefs

Cf. A061511 - A061522, A061746 - A061750; A061581 - A061587.

Cf. also A010785.

Sequence in context: A029950 A061507 A046497 * A356750 A083964 A340439

Adjacent sequences: A061509 A061510 A061511 * A061513 A061514 A061515

Keyword

base,nonn

Author

Amarnath Murthy, May 08 2001

Extensions

More terms from Larry Reeves (larryr(AT)acm.org), May 11 2001

Status

approved