12345654321
domain: N
Appears in sequences
- Wonderful Demlo numbers: a(n) = ((10^n - 1)/9)^2.at n=5A002477
- Concatenation of sequence (1, 2, ..., floor((n-1)/2), floor(n/2), floor(n/2)-1, ..., 1) for n >= 1.at n=10A007907
- Squares whose consecutive digits differ by 1.at n=9A048411
- Palindromes whose square root is a palindrome.at n=25A057136
- Odd number of digits palindrome based on sequential digits.at n=5A057139
- Squares whose consecutive digits vary by at most 1.at n=24A061850
- Smallest square beginning with concatenation of first n natural numbers.at n=5A068117
- a(1) = 9; a(n) = smallest multiple of a(n-1) which is a palindromic square.at n=3A069501
- Smallest multiple of prime(n) of the form 123...(k-1) k (k-1)...321 ( a concatenation of natural numbers from 1 to k and back to 1), or 0 if no such number exists.at n=3A077186
- Smallest multiple of prime(n) of the form 123...(k-1) k (k-1)...321 ( a concatenation of natural numbers from 1 to k and back to 1), or 0 if no such number exists.at n=5A077186
- Smallest concatenation 123...(k-1) k (k-1)...321 (a concatenation of natural numbers from 1 to k and back to 1) that is a multiple of 2n-1, or 0 if no such number exists.at n=3A077189
- Smallest concatenation 123...(k-1) k (k-1)...321 (a concatenation of natural numbers from 1 to k and back to 1) that is a multiple of 2n-1, or 0 if no such number exists.at n=6A077189
- Wonderful Demlo numbers A002477 whose digit sums are squares.at n=5A080162
- Powers of 111111.at n=2A109716
- Giza numbers.at n=35A134810
- a(n) is obtained by starting with 1, sequentially concatenating all decimal numbers up to n, and then, starting from n-1, sequentially concatenating all decimal numbers down to 1.at n=5A173426
- Squares of A057148 taken as decimal numbers.at n=14A176923
- Giza nonprimes.at n=28A182775
- Concatenation of the palindromic numbers (A002113) in increasing order up to the n-th term and then in decreasing order.at n=5A261570
- a(n) = A128921(n)^2.at n=27A319483