a(n) = 99*A002275(n) (Repunits).

Erroneous version of A001232.

0, 99, 1089, 10989, 109989, 1099989, 10999989, 109999989, 1099999989, 10999999989, 109999999989, 1099999999989, 10999999999989, 109999999999989, 1099999999999989, 10999999999999989, 109999999999999989, 1099999999999999989, 10999999999999999989, 109999999999999999989, 1099999999999999999989

1089, 10989, 109989, 1099989, 10999989, 109999989

0,2

1,1

For n>0, the following mapping leads to a(n): Start with any (n+1)-digit number where the difference between the first and last digits of the number is greater than unity. Rewrite this number with the first and last digits interchanged. Subtract the smaller number from the greater one. Rewrite the result with the first and last digit interchanged. Add these two recent numbers. The result is a(n).

To remark, if you start with a number where the difference between the first and last digits of the number equals unity, the mapping described leads to A086573(n) = 18*A002275(n).

For n>1, the first two digits are always 10, the last two are 89. The number of 9's separating the first two digits from the last two digits is always n-2.

For n>1, this sequence is a subset of A001232.

Royal Vale Heath, Mathemagic. Magic, Puzzles, Games with Numbers, Dover, 1953, pp. 80-81 (Always the same number).

seq(99*(10^n-1)/9, n=0..20);

Cf. A001232, A002275, A086573.

nonn,base,changed

dead

Martin Renner, Jun 28 2020

editing

approved

proposed

editing

editing

proposed

Erroneous version of A001232.

a(n) = 99*A002275(n) (Repunits).

0, 99, 1089, 10989, 109989, 1099989, 10999989, 109999989, 1099999989, 10999999989, 109999999989, 1099999999989, 10999999999989, 109999999999989, 1099999999999989, 10999999999999989, 109999999999999989, 1099999999999999989, 10999999999999999989, 109999999999999999989, 1099999999999999999989

1,1

0,2

For n>0, the following mapping leads to a(n): Start with any (n+1)-digit number where the difference between the first and last digits of the number is greater than unity. Rewrite this number with the first and last digits interchanged. Subtract the smaller number from the greater one. Rewrite the result with the first and last digit interchanged. Add these two recent numbers. The result is a(n).

To remark, if you start with a number where the difference between the first and last digits of the number equals unity, the mapping described leads to A086573(n) = 18*A002275(n).

For n>1, the first two digits are always 10, the last two are 89. The number of 9's separating the first two digits from the last two digits is always n-2.

For n>1, this sequence is a subset of A001232.

Royal Vale Heath, Mathemagic. Magic, Puzzles, Games with Numbers, Dover, 1953, pp. 80-81 (Always the same number).

seq(99*(10^n-1)/9, n=0..20);

Cf. A001232, A002275, A086573.

dead

nonn,base

Martin Renner, Jun 28 2020

approved

editing

Erroneous version of A001232.

1089, 10989, 109989, 1099989, 10999989, 109999989

1,1

dead

approved