21100

Appears in sequences

• Expansion of Product_{m>=1} (1 + q^m)^25.at n=4A022589
• Multiples of 4 whose digits add to 4.at n=21A063997
• Numbers n such that phi(reversal(n)) = reversal(phi(n)). Ignore leading 0's.at n=19A069282
• Square roots of A069191, sorted.at n=30A070223
• Full Łukasiewicz word for each rooted plane tree (interpretation e in Stanley's exercise 19) encoded by A014486 (or A063171).at n=19A079436
• Factorial expansions of the entries in A085219.at n=42A085221
• Factorial expansions of the entries in A085220.at n=38A085222
• Sum of squares of four consecutive primes.at n=18A133524
• Squares in lunar arithmetic in base 3 written in base 3.at n=21A171396
• Squares in lunar arithmetic in base 4 written in base 4.at n=36A171460
• Numbers of rank 11 in the poset of lunar numbers.at n=27A191753
• Sophie Germain 5-almost primes.at n=42A211162
• Determinant of the n X n matrix with (i,j)-entry equal to 1 or 0 according as 2*(i + j) - 1 is prime or not.at n=33A228616
• 29-gonal numbers: a(n) = n*(27*n-25)/2.at n=40A255187
• a(n), n>1, is the smallest number k whose symmetric representation of sigma(k) has two parts and has a larger number of legs in its two parts than a(n-1); a(1)=3.at n=28A279105
• Numbers that are not the difference of two binary palindromes (A006995).at n=43A290393
• List of binary words of lengths 0, 1, 2, etc., including empty word, each prefixed by a 2.at n=27A319953
• Modified Sisyphus function of order 4: a(n) is the concatenation of (number of digits of n)(number digits of n congruent to 0 modulo 4)(number of digits of n congruent to 1 modulo 4)(number of digits of n congruent to 2 modulo 4)(number of digits of n congruent to 3 modulo 4).at n=10A352751
• Modified Sisyphus function of order 4: a(n) is the concatenation of (number of digits of n)(number digits of n congruent to 0 modulo 4)(number of digits of n congruent to 1 modulo 4)(number of digits of n congruent to 2 modulo 4)(number of digits of n congruent to 3 modulo 4).at n=14A352751
• Modified Sisyphus function of order 4: a(n) is the concatenation of (number of digits of n)(number digits of n congruent to 0 modulo 4)(number of digits of n congruent to 1 modulo 4)(number of digits of n congruent to 2 modulo 4)(number of digits of n congruent to 3 modulo 4).at n=18A352751