A323645 a(n) is the number of visible faces in the perspective view of the stepped pyramid with n levels described in A245092.

3, 6, 12, 17, 21, 28, 32, 39, 46, 56, 60, 69, 73, 81, 92, 103, 107, 118, 122

Offset: 1

Author

Omar E. Pol, Mar 20 2019

Keywords

• nonn
• more

Comments

The shape of the n-th level of the pyramid allows us to know if n is prime (see the Formula section).

For more sequences that we can find in the pyramid see A262626.

Links

• Omar E. Pol, Perspective view of the stepped pyramid (levels: 1..16) and A000203

Crossrefs

Cf. A000040, A000203, A024916, A196020, A215848, A224880, A235791, A236104, A237048, A237270, A237271, A237593, A245092, A262626, A299692 (total area).

Formula

a(n) = a(n-1) + 4 iff n is a prime > 3 (A215848).

a(n) = A325300(n) - 3. - Omar E. Pol, Apr 17 2019

Extensions

a(18)-a(19) from Omar E. Pol, Apr 18 2019