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A260586 Concatenated sums of pairs of adjacent digits in the concatenation of the numbers from 1 to n. 1
0, 0, 3, 35, 357, 3579, 357911, 35791113, 3579111315, 357911131517, 357911131517101, 35791113151710112, 3579111315171011223, 357911131517101122334, 35791113151710112233445, 3579111315171011223344556, 357911131517101122334455667, 35791113151710112233445566778 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
COMMENTS
The underlying sequence to calculate the sums of the pairs of adjacent digits is A007908 = (0, 1, 12, 123, 1234, 12345, 123456, 1234567, 12345678, 123456789, 12345678910, 1234567891011, ...).
LINKS
EXAMPLE
For n=3, A007908(3) is 123, and (1+2)_(2+3) gives 35, so a(3)=35.
For n=4, A007908(4) is 1234, and (1+2)_(2+3)_(3+4) gives 357, so a(4)=357.
MATHEMATICA
Table[FromDigits[Flatten[IntegerDigits/@Total/@Partition[Flatten[ IntegerDigits/@ Range[n]], 2, 1]]], {n, 0, 20}] (* Harvey P. Dale, Dec 18 2019 *)
PROG
(PARI) b(n)=my(s=""); for(k=1, n, s=Str(s, k)); eval(s);
a(n) = {my(x = b(n)); if (x==0, d = [0], d = digits(x)); my(s=""); for (k=1, #d-1, s = concat(s, d[k] + d[k+1]); ); if (!#s, 0, eval(s)); } \\ Michel Marcus, Jul 30 2015
CROSSREFS
Cf. A007908.
Sequence in context: A198961 A112488 A221922 * A089933 A086043 A221774
KEYWORD
easy,base,nonn,less
AUTHOR
Marco Ripà, Jul 29 2015
STATUS
approved

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Last modified May 25 16:13 EDT 2024. Contains 372800 sequences. (Running on oeis4.)