27270

Appears in sequences

• Coefficients of Jacobi cusp form of index 1 and weight 10.at n=35A003784
• A hierarchical sequence (S(W3{2,2}cc) - see A059126).at n=8A059138
• Numbers k that divide phi(k)^2 + sigma(k)^2.at n=36A068484
• Pentagonal numbers (A000326) whose digit reversal is the product of 2 palindromes greater than 1.at n=16A115703
• Pentagonal numbers > 0 which are not the difference of two other pentagonal numbers > 0.at n=15A135769
• Pentagonal numbers > 0 which are not the difference of two larger pentagonal numbers.at n=22A136113
• One-half of averages of twin prime pairs of A001318.at n=18A154565
• Number of (w,x,y) with all terms in {0,...,n} and w<=x+y and x<=y.at n=39A212983
• Pentagonal numbers that are also Niven numbers.at n=36A242043
• a(n) = 3*n*(9*n - 1)/2.at n=45A268351
• Pentagonal numbers (A000326) in which parity of digits alternates.at n=21A297644
• a(n) = (A001359(n+1)^2 - 1)/24, where A001359 = lesser of twin primes; or: pentagonal numbers (A000326) whose indices are twin ranks (A002822).at n=29A308344
• Number of regions in a regular n-gon with all diagonals drawn whose edges all have the same number of facing edges.at n=51A351129
• Pentagonal numbers that are abundant.at n=44A379264