30001

Appears in sequences

• a(n) = floor(n(n-1)(n-2)(n-3)/19).at n=29A011929
• n written in fractional base 6/3.at n=49A024636
• Numbers k such that k^2+k+7 is a palindrome.at n=13A027722
• Numbers n with property that n is a substring of its base 5 representation.at n=16A038105
• a(n) = sqrt(A077204(n)).at n=8A077205
• Numbers n such that there are (presumably) ten palindromes in the Reverse and Add! trajectory of n.at n=3A090071
• Expansion of (1-x)^2/((1-x)^3 - 4*x^3).at n=12A097123
• Let P(i) = i-th prime. To get a(n), factor P(n)-1 as a product of primes, then concatenate the exponents.at n=23A097463
• a(1) = 1; for n>1, a(n) = smallest number > a(n-1) such that last digit of a(n-1) + first digit of a(n) = 3.at n=13A098408
• Lexicographically earliest increasing sequence whose k-th digit is the absolute difference between the two digits touching the k-th comma.at n=15A102663
• Greater of number pair whose squares are reversals of each other, with no leading zeros allowed.at n=28A106324
• Semiprimes in A056107.at n=26A113525
• Numbers k such that k and k^2 use only the digits 0, 1, 3, 6 and 9.at n=53A136850
• a(n) = 48*n^2 + 1.at n=25A158638
• a(n) = 3*10^n + 1.at n=4A199683
• A239461(n) / n^2.at n=29A239464
• Least positive integer m with pi(m*n) = phi(m), where pi(.) is the prime-counting function and phi(.) is Euler's totient function.at n=10A247601
• Numbers n which are both happy (A007770) and bihappy (A257795) numbers.at n=33A257950
• Sequence A261220 shown in factorial base: a(n) = A007623(A261220(n)).at n=47A260743
• Numbers k such that Rd(k) == k (mod Ld(k)), where Rd(k) = A067079 and Ld(k) = A067080.at n=51A324321