1222222221

Appears in sequences

• All possible products in increasing order of two distinct members of the unary sequence 1, 11, 111, 1111, 11111, ...given by A000042.at n=21A077488
• Expansion of g.f. x*(1+10*x)/((1-x)*(1-10*x^2)).at n=18A094623
• Expansion of g.f. x*(1+11*x+x^2)/((1-x)*(1+x)*(1-10*x^2)).at n=18A094624
• a(n) = n 2's sandwiched between two 1's.at n=8A132583
• a(n) = 111111111 * n.at n=10A172525
• Numbers that can be written as a product of distinct repunits.at n=27A334131
• a(1) = 1; for n > 1, a(n) is the smallest unused positive number such that a(n), |a(n) - a(n-1)| and a(1) + ... +a(n) are all palindromes.at n=43A376856