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A247796 From right to left in decimal representation of n: replace each maximal set of adjacent digits with their sum, if this sum is less than 10. 3
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 19, 2, 3, 4, 5, 6, 7, 8, 9, 28, 29, 3, 4, 5, 6, 7, 8, 9, 37, 38, 39, 4, 5, 6, 7, 8, 9, 46, 47, 48, 49, 5, 6, 7, 8, 9, 55, 56, 57, 58, 59, 6, 7, 8, 9, 64, 65, 66, 67, 68, 69, 7, 8, 9, 73, 74, 75, 76, 77 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 0..10000

FORMULA

a(n) <= n; a(A248013(n)) = A248013(n); a(A248014(n)) < A248014(n);

a(n) =  a(a(n)) = a(A004719(n)) = a(n * 10^k).

EXAMPLE

7654321: 7654[321] -> 7654[3+2+1] -> 76546 -> 76[54]6 -> 76[5+4]6 -> 7696 = a(7654321);

1234567: 123[45]67 -> 123[4+5]67 -> 123967 -> [123]967 -> [1+2+3]967 -> 6967 = a(1234567);

1111111: [1111111] -> [1+1+1+1+1+1+1] -> 7 = a(1111111);

a(7777777) = 7777777;

90909: 909[09] -> 909[0+9] -> 9099 -> 9[09]9 -> 9[0+9]9 -> 999 = a(90909);

20202: [20202] -> [2+0+2+0+2] -> 6 = a(20202).

PROG

(Haskell)

a247796 = f 0 where

   f s 0 = s

   f s x = if s + d < 10 then f (s + d) x' else (f d x') * 10 + s

           where (x', d) = divMod x 10

(PARI) A247796(n, d=digits(n))={forstep(k=#d, 2, -1, if(d[k-1]+d[k]<10, d[k-1]+=d[k]; d=d[^k])); fromdigits(d)} /* or: (about 10% faster) */

A247796(n, u=1)={until(n<10*u*=10, my(m=n\u); while(m>9&&sumdigits(m%100)<10, m=vecsum(divrem(m, 10)); n=m*u+n%u)); n} \\ Trying to reduce the number of redefinitions of n yields slower code. M. F. Hasler, Jan 29 2018

CROSSREFS

Cf. A248013, A248014.

Sequence in context: A080463 A209685 A114570 * A115026 A101337 A135208

Adjacent sequences:  A247793 A247794 A247795 * A247797 A247798 A247799

KEYWORD

nonn,base,look

AUTHOR

Reinhard Zumkeller, Oct 08 2014

EXTENSIONS

Edited by M. F. Hasler, Jan 29 2018

STATUS

approved

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Last modified August 22 02:44 EDT 2019. Contains 326169 sequences. (Running on oeis4.)