122221

Appears in sequences

• a(n) = n^2 written in base 3.at n=22A001738
• Divisors of 9999999999.at n=25A027895
• k th digit of a(n) = number of different digits within 2 places of k (not including k).at n=19A039987
• k th digit of a(n) is the number of different digits within 3 of k (not including k).at n=17A039989
• k th digit of a(n) is the number of different digits within 4 of k (not including k).at n=17A039990
• Palindromes that are the sum of two shorter palindromes.at n=16A062696
• a(n) = (10^n - 1)/9*prime(n).at n=4A064008
• All possible products in increasing order of two distinct members of the unary sequence 1, 11, 111, 1111, 11111, ...given by A000042.at n=7A077488
• Diagonal of A083464.at n=35A083465
• Expansion of g.f. x*(1+10*x)/((1-x)*(1-10*x^2)).at n=10A094623
• Expansion of g.f. x*(1+11*x+x^2)/((1-x)*(1+x)*(1-10*x^2)).at n=10A094624
• Concatenate (1,n,n,1).at n=22A100846
• List of molecules in Hintze-Adami artificial chemistry (see comments for definition).at n=19A101145
• n expressed in Fibonacci binary-like number system using only 1's and 2's.at n=30A108960
• a(n) = n 2's sandwiched between two 1's.at n=4A132583
• Numbers k such that gcd(k^2, reverse(k^2)) = k.at n=18A175823
• Numbers for which the sum of reciprocals of square of digits is an integer.at n=16A182452
• Algebraic cofactor of n-th repunit A002275(n).at n=9A204848
• Dates after Jan 01 00 in chronological order which are palindromic when they are written according to the format MMDDYY (American standard, short). Leading zeros of the terms are suppressed.at n=9A210895
• Triangle read by rows in which row n lists the binary words of length n over the alphabet {1,2} with no initial repeats.at n=34A211029