1,3
Cf. A000720.
Sequence in context: A128014 A135401 A129881 this_sequence A081123 A056038 A076929
Adjacent sequences: A132366 A132367 A132368 this_sequence A132370 A132371 A132372
easy,nonn
Giovanni Teofilatto (g.teofilatto(AT)tiscalinet.it), Nov 09 2007
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