21540

Appears in sequences

• Number of partitions into one kind of 1's, two kinds of 2's, and three kinds of 3's.at n=42A002597
• Numbers which are the sum of their proper divisors containing the digit 7.at n=28A059466
• Sequence of sums based on primes = 7 mod 8.at n=30A060108
• Numbers n such that [A070080(n), A070081(n), A070082(n)] is an isosceles integer triangle with integer area.at n=33A070145
• Pentagonal numbers for which the sum of the digits is also a pentagonal number.at n=15A117709
• Pentagonal numbers for which both the sum of the digits and the product of the digits are pentagonal numbers.at n=8A117711
• Number of n X n symmetric binary matrices containing no more than two 1s in any 3 X 3 sub-block.at n=7A139010
• Triangle read by rows: expansion of p(x,n)=If[n == 0, 1, (x + 1)^n + 2^(n+1)*Sum[Binomial[n-m, m]*x^m*(1 + x^(n - 2*m)), {m, 1, n - 1}]].at n=47A146774
• Triangle read by rows: expansion of p(x,n)=If[n == 0, 1, (x + 1)^n + 2^(n+1)*Sum[Binomial[n-m, m]*x^m*(1 + x^(n - 2*m)), {m, 1, n - 1}]].at n=52A146774
• a(n) = n*(n + 1)*(3*n^2 + 3*n - 2)/8.at n=15A236770
• The positions of records in A236747.at n=11A237267
• Pentagonal numbers that are also Niven numbers.at n=32A242043
• Least integer m > 0 with pi(m*n) = sigma(m) + sigma(n), where pi(.) and sigma(.) are given by A000720 and A000203 respectively.at n=30A247673
• Prime sieve of e.at n=34A248804
• Numbers equidistant from twin prime pairs that are also equidistant from numbers equidistant from twin prime pairs.at n=26A260517
• a(n) = 3*n*(9*n - 1)/2.at n=40A268351
• a(n) = a(n-1) + 3*a(n-2) - 2*a(n-3) - a(n-4) for n >= 4, where a(0) = 2, a(1) = 4, a(2) = 7, a(3) = 12.at n=15A288317
• Pentagonal numbers divisible by 4.at n=30A298397
• Partial sums of A092181.at n=7A302562
• Gaps between first elements of prime quintuples of the form (p, p+2, p+6, p+12, p+14). The quintuples are abutting: twin/cousin/sexy/twin pairs.at n=27A342502