A019524 Duplicate terms of A007908.

11, 1212, 123123, 12341234, 1234512345, 123456123456, 12345671234567, 1234567812345678, 123456789123456789, 1234567891012345678910, 12345678910111234567891011, 123456789101112123456789101112

Offset: 1

Author

R. Muller

Keywords

• nonn

References

• F. Iacobescu, Smarandache Partition Type and Other Sequences, Bull. Pure Appl. Sciences, Vol. 16E, No. 2 (1997), pp. 237-240.

Links

• Eric Weisstein's World of Mathematics, Smarandache Sequences
• F. Smarandache, Collected Papers, Vol. II
• F. Smarandache, Sequences of Numbers Involved in Unsolved Problems.

Formula

a(n) = A007908(n)*(1 + 10^A058183(n)) = (n + a(n - 1)*10^L(n)/(1 + 10^(n*L(n - 1) - (10^L(n - 1) - 1)/9)))*(1 + 10^((n + 1)*L(n) - (10^L(n) - 1)/9)) where L(n) = floor(log_10(10n)). - Henry Bottomley, Nov 17 2000 (may need to be adapted for change in offset)