27888

Appears in sequences

• a(n) = (n^2 - 1)*(n^2 - 3).at n=13A033596
• Call two meanders from A005316 equivalent if they differ by a reflection in the Y axis (if n even) or by reflections in the X or Y axes (if n odd). Sequence gives number of inequivalent meanders with n crossings.at n=14A077055
• a(n) = (prime(n)-1)*(prime(n)+1).at n=38A084920
• Convolution of the prime numbers with phi(n).at n=41A086734
• Numbers that have exactly seven prime factors counted with multiplicity (A046308) whose digit reversal is different and also has 7 prime factors (with multiplicity).at n=15A109027
• Numbers whose square starts with 4 identical digits.at n=27A132391
• Eight times hexagonal numbers: a(n) = 8*n*(2*n-1).at n=42A152750
• Numbers in cycles of RATS sequences.at n=20A161596
• A triangle related to the a(n) formulas of the rows of the ED4 array A167584.at n=23A167591
• The third left hand column of triangle A167591.at n=4A167593
• a(n) = Sum_{k=0..n} binomial(n,k)^2*binomial(2k,k+1).at n=6A228514
• a(n) is the smallest k such that phi(k) = reverse(k-n), or 0 if no such k exists.at n=17A241473
• G.f. A(x) satisfies: x = A(x) * (1 - A(x)) * (1 - 3*A(x)).at n=5A250885
• Numbers in 2-cycles of RATS sequences.at n=7A275218
• T(n,k) = number of linear arrays of n 1's, n -1's, and k 0's such that no two adjacent elements are equal.at n=76A283613
• Numbers of the form p^2 - 1 where p is a prime of the form 3*k-1 (A003627).at n=19A301812
• a(n) = 144*n^2 - 24*n (n>=1).at n=13A305072
• Numbers whose square starts with exactly 4 identical digits.at n=26A346940
• Indices of 0 in A348295: numbers m such that Sum_{k=1..m} (-1)^(floor(k*(sqrt(2)-1))) = Sum_{k=1..m} (-1)^A097508(k) = 0.at n=39A348299
• Numbers sandwiched between two semiprimes, one of which is a square.at n=29A358686